The incident took place late last month in Dahanu area of the district adjoining Mumbai.
Sub-Inspector R C Patil of Dahanu Police Station said the 14-year-old victim, a resident of Nayak Pada, was returning home from school in afternoon on a bicycle when the accused, who was on a motorbike, waylaid her.
He forced the minor to get onto his motorbike and took her to a forest near village Chari, where he sexually assaulted her, police said, quoting a complaint filed by the girl yesterday.
Offences under relevant sections of IPC and Protection of Children from Sexual Offences Act have been filed and a hunt has been launched for the accused, they added.