Kieran Hawkshaw, of Murrells Court, Norwich, also pleaded guilty to assault occasioning actual bodily harm when he appeared at Norwich Crown Court.
A 26-year-old woman was attacked as she walked home from the city along Drayton Road on Sunday 6 September. She suffered facial injuries.
Hawkshaw was remanded in custody and will be sentenced on Friday 13 November.
A 25-year-old man has admitted the attempted rape of a woman in Norfolk.