Provided is an autonomous vehicle assistance device and method that may precisely determine a position of a vehicle based on input position error information. The autonomous vehicle assistance device includes a communicator configured to receive satellite navigation information, correction information transmitted from a base station, and position error information transmitted from a fixed body, and a vehicle position determiner configured to calculate first position information corresponding to the received satellite navigation information and correction information and to calculate a current position of a vehicle by correcting the first position information based on the position error information.