Tarō Hirai was born in Nabari, Mie Prefecture in 1894, where his grandfather had been a samurai in the service of Tsu Domain. The family moved to what is now Kameyama, Mie, and from there to Nagoya when he was age two. He studied economics at Waseda University starting in 1912. After graduating in 1916 with a degree in economics he worked a series of odd jobs, including newspaper editing, drawing cartoons for magazine publications, selling soba noodles as a street vendor, and working in a used bookstore.

In 1923 he made his literary debut by publishing the mystery story “The Two-Sen Copper Coin” (二銭銅貨, Ni-sen dōka) under the pen name “Edogawa Ranpo” (pronounced quickly, this humorous pseudonym sounds much like the name of the American pioneer of detective fiction, Edgar Allan Poe, whom he admired). The story appeared in the magazine Shin Seinen, a popular magazine written largely for an adolescent audience. Shin Seinen had previously published stories by a variety of Western authors including Poe, Arthur Conan Doyle, and G. K. Chesterton, but this was the first time the magazine published a major piece of mystery fiction by a Japanese author. Some, such as James B. Harris (Ranpo’s first translator into English), have erroneously called this the first piece of modern mystery fiction by a Japanese writer, but well before Ranpo entered the literary scene in 1923, a number of other modern Japanese authors such as Ruikō Kuroiwa, Kidō Okamoto, Jun’ichirō Tanizaki, Haruo Satō, and Kaita Murayama had incorporated elements of sleuthing, mystery, and crime within stories involving adventure, intrigue, the bizarre, and the grotesque. What struck critics as new about Ranpo’s debut story “The Two-Sen Copper Coin” was that it focused on the logical process of ratiocination used to solve a mystery within a story that is closely related to Japanese culture. The story involves an extensive description of an ingenious code based on a Buddhist chant known as the “nenbutsu” as well as Japanese-language Braille.

In 1939, two years after the Marco Polo Bridge Incident and the outbreak of the Second Sino-Japanese War in 1937, Edogawa was ordered by government censors to drop his story “The Caterpillar” (芋虫, Imo Mushi), which he had published without incident a few years before, from a collection of his short stories that the publisher Shun’yōdō was reprinting. “The Caterpillar” is about a veteran who was turned into a quadriplegic and so disfigured by war that he was little more than a human “caterpillar”, unable to talk, move, or live by himself. Censors banned the story, apparently believing that the story would detract from the current war effort. This came as a blow to Ranpo, who relied on royalties from reprints for income. (The short story inspired director Kōji Wakamatsu, who drew from it his movie Caterpillar, which competed for the Golden Bear at the 60th Berlin International Film Festival.)

Over the course of World War II, especially during the full-fledged war between Japan and the US that began after in 1941, Edogawa was active in his local neighborhood organization, and he wrote a number of stories about young detectives and sleuths that might be seen as in line with the war effort, but he wrote most of these under different pseudonyms as if to disassociate them with his legacy. In February 1945, his family was evacuated from their home in Ikebukuro, Tokyo to Fukushima in northern Japan. Edogawa remained until June, when he was suffering from malnutrition. Much of Ikebukuro was destroyed in Allied air raids and the subsequent fires that broke out in the city, but miraculously, the thick, earthen-walled warehouse which he used as his studio was spared, and still stands to this day beside the campus of Rikkyo University.

Another of his interests, especially during the late 1940s and 1950s, was bringing attention to the work of his dear friend Jun’ichi Iwata (1900–1945), an anthropologist who had spent many years researching the history of homosexuality in Japan. During the 1930s, Edogawa and Iwata had engaged in a light-hearted competition to see who could find the most books about erotic desire between men. Edogawa dedicated himself to finding books published in the West and Iwata dedicated himself to finding books having to do with Japan. Iwata died in 1945, with only part of his work published, so Edogawa worked to have the remaining work on queer historiography published.

In the postwar period, Edogawa dedicated a great deal of energy to promoting mystery fiction, both in terms of the understanding of its history and encouraging the production of new mystery fiction. In 1946, he put his support behind a new journal called Jewels (宝石, Hōseki) dedicated to mystery fiction, and in 1947, he founded the Detective Author’s Club (探偵作家クラブ, Tantei sakka kurabu), which changed its name in 1963 to the Mystery Writers of Japan (日本推理作家協会, Nihon Suiri Sakka Kyōkai). In addition, he wrote a large number of articles about the history of Japanese, European, and American mystery fiction. Many of these essays were published in book form. Other than essays, much of his postwar literary production consisted largely of novels for juvenile readers featuring Kogorō Akechi and the Boy Detectives Club.

In the postwar period, a large number of Edogawa’s books were made into films. The interest in using Edogawa’s literature as a departure point for creating films has continued well after his death. Edogawa, who suffered from a variety of health issues, including atherosclerosis and Parkinson’s disease, died from a cerebral hemorrhage at his home in 1965. His grave is at the Tama Cemetery in Fuchu, near Tokyo.