A parking assist apparatus includes: an entry guidance unit configured to, upon receiving a parking request for guiding an autonomous driving vehicle to a parking area in a parking lot, guide the autonomous driving vehicle from an entry initial position, which is a position of the autonomous driving vehicle immediately before starting an entry guidance, to the parking area, as a first target position; and a cancellation guidance unit configured to, upon receiving a parking cancellation request for cancelling the parking request before the autonomous driving vehicle arrives at the first target position: set a second target position that is a different position in the parking lot according to a positional relationship of a current position of the autonomous driving vehicle relative to the entry initial position; and guide the autonomous driving vehicle to the second target position.