The incident took place in the early hours of Monday. The bus was going from Mayurbhanj to Cuttack city, about 25 km from here.
Although there were about a dozen passengers in the bus, none was awake when the rape took place. The victim could not raise an alarm as her mouth was gagged by the accused, who later threatened to kill her if she dared to speak about it to any one, Jena said.
The incident came to light only after the victim got off from the bus at Cuttack and some people spotted her crying and took her to a police station.
"Police apprehended the helper on the basis of a complaint lodged by the victim. He has confessed to the crime. Medical examinations on the victim has been conducted," the police officer said.
The victim hails from Mayurbhanj, about 250 km from the state capital Bhubaneswar, and works as a maid in Cuttack.