The incident took place at Ajgari village late last night as the accused in an inebriated condition took the child to a nearby place and raped her, Deputy Superintendent of Police Vijay Kumar said.
The girl was found lying unconscious by her family members who then rushed her to a hospital for treatment, he added.
Acting on a complaint filed by the family, the police arrested the accused from Motihari town and booked him under relevant sections of law after he confessed to the deed.