The 48 men from 18 prefectures include teachers and firefighters, according to the joint investigation team of the Chiba and Aichi prefectural police.
The men are suspected of using Cabos file-swapping software to publicly circulate the pornographic images and video on the Internet last year, according to the police.
Of the 48, three, including a teacher at a private junior high school in Tokyo in his 30s, were arrested by the Chiba prefectural police. The teacher is still being questioned by investigators on a voluntary basis after being released on bail, while the other two have been fined 500,000 yen.
The police have sent papers on the other men to prosecutors, they said.
The joint team initiated a cyber-patrol after the police received a report from an acquaintance of the girl that the images and video had been posted on the Internet, it said