Provided is a parking assistance device capable of setting a parking target position without placing a burden on a driver. The parking assistance device includes: a ground object detection unit configured to detect a ground object that defines a parking stall in a predetermined detection region set in advance on a lateral side of a vehicle; a parking stall calculation unit configured to, based on the ground object detected by the ground object detection unit, calculate a parking stall that exists in the detection region; and a target parking stall setting unit configured to, among the parking stalls calculated by the parking stall calculation unit, sets a parking stall in a width direction of the vehicle in a view from a driver's seat of the vehicle as a target parking stall.