A parking assistance device (100a, 100b) being configured to perform at least steering control so that a subject vehicle moves along a target path toward a recognized parking space; when an obstacle that is approaching the subject vehicle has been detected, calculate a predicted collision position at which the subject vehicle will collide with the obstacle, wherein the predicted collision position is a position at which a predicted progression path of the obstacle and the target path intersect, and furthermore is a position at which the subject vehicle and the obstacle arrive approximately simultaneously; and set a margin distance (DIST) according to the driving behavior of the subject vehicle; wherein the parking assistance device (100a; 100b) is further configured to perform (a) or (b): (a) on the basis of the margin distance (DIST) and the predicted collision position, calculate a stop position upon the target path that is set before the predicted collision position by the margin distance (DIST); and perform speed control so that the subject vehicle stops at the stop position that has been calculated, (b) output an alarm upon arrival at an alarm position that is a position upon the target path before the predicted collision position, and that is at the margin distance (DIST) before the predicted collision position; and wherein: the target path includes a forward path along which the subject vehicle is moved forward from its current position to a changeback position, and a backward path along which the subject vehicle performs motion in a straight line and turning while being moved backward from the changeback position to the parking space; the driving behavior includes moving in a straight line or turning; the margin distance (DIST)) upon the turning path is set to be greater than the margin distance (DIST) upon the straight line path; and the margin distance (DIST) upon the backward path is greater than the margin distance (DIST) upon the forward path. perform at least steering control so that a subject vehicle moves along a target path toward a recognized parking space; when an obstacle that is approaching the subject vehicle has been detected, calculate a predicted collision position at which the subject vehicle will collide with the obstacle, wherein the predicted collision position is a position at which a predicted progression path of the obstacle and the target path intersect, and furthermore is a position at which the subject vehicle and the obstacle arrive approximately simultaneously; and set a margin distance (DIST) according to the driving behavior of the subject vehicle; wherein the parking assistance device (100a; 100b) is further configured to perform (a) or (b): (a) on the basis of the margin distance (DIST) and the predicted collision position, calculate a stop position upon the target path that is set before the predicted collision position by the margin distance (DIST); and perform speed control so that the subject vehicle stops at the stop position that has been calculated, (b) output an alarm upon arrival at an alarm position that is a position upon the target path before the predicted collision position, and that is at the margin distance (DIST) before the predicted collision position; (a) on the basis of the margin distance (DIST) and the predicted collision position, calculate a stop position upon the target path that is set before the predicted collision position by the margin distance (DIST); and perform speed control so that the subject vehicle stops at the stop position that has been calculated, (b) output an alarm upon arrival at an alarm position that is a position upon the target path before the predicted collision position, and that is at the margin distance (DIST) before the predicted collision position; the target path includes a forward path along which the subject vehicle is moved forward from its current position to a changeback position, and a backward path along which the subject vehicle performs motion in a straight line and turning while being moved backward from the changeback position to the parking space; the driving behavior includes moving in a straight line or turning; the margin distance (DIST)) upon the turning path is set to be greater than the margin distance (DIST) upon the straight line path; and the margin distance (DIST) upon the backward path is greater than the margin distance (DIST) upon the forward path.