A parking assistance device includes: a ground object detection unit configured to, in a predetermined detection region set in advance in at least a portion of the vehicle periphery, perform detection of a ground object defining a parking stall in which garage parking is to be performed; an end portion specification unit configured to specify an end portion of the ground object detected by the ground object detection unit, the end portion being located on an entrance side of the parking stall; and a target parking stall setting unit configured to set, based on the end portion on the entrance side specified by the end portion specification unit, a corner portion of a rectangular parking frame that defines a target parking stall in which the vehicle is to be parked, and set the parking frame to extend from the corner portion in the depth direction of the parking stall.