The accused, identified as Ashok Panjwani (40), was arrested yesterday based on a complaint lodged by the victim, Kotwali police SHO Yadumani Sidar said.
Panjwani, a resident of Kashinagar locality, had married the victim's mother few years back and since then they were living together.
On Friday (December 11) night, the accused went into the room of her stepdaughter and allegedly raped her. The girl later narrated her ordeal to her mother who then approached the police, the SHO said.
The victim was also molested by the accused in the past, but she refrained from telling her mother about it fearing her stepfather, he said.