The incident, which took place on August four, came to light when the girl's mother lodged an FIR at Kotwali Women's police station today.
The 13-year-old girl, a student of local Tarak Das High School, was raped by Kala Chand Mondal while she was going to an agricultural field near her residence on the very day, they said.
A student of class VII, the girl had initially suppressed the matter out of fear, but narrated her ordeal to her grandmother yesterday.
The accused was arrested today, who later admitted that he was in an inebriated condition when he had committed the offence, police added.