A parking assistance device comprising: a route determination unit that determines a route from an initial position of a vehicle to a target parking position at a time of assisting the vehicle to be parked in a parking area, wherein the route determination unit includes, a first generation unit that generates a first circumference which is tangent to a straight line passing though the initial position and extending along a forward direction of the vehicle, and a second generation unit that generates a second circumference having a tangent line which is a line passing through a rear position of the vehicle positioned at a rear direction of the target parking position in the forward direction of the vehicle and extending along the forward direction of the vehicle, and having a radius as a turning radius at the time of minimum turning of the vehicle, wherein a part of the first circumference functions as a part of the route, and a part of a third circumference resulting from moving the second circumference along the forward direction of the vehicle functions as the route subsequent to the first circumference, and the second generation unit generates the third circumference resulting from moving the second circumference until an avoidance circle having a center at a corner portion of an obstacle disposed in the front direction of the parking area and having a radius as a predetermined distance and an outer circumference circle through which an end portion of the vehicle moving along the third circumference passes, become tangent to each other, characterized in that the first generation unit regenerates the first circumference which is tangent to the third circumference and generates the first circumference in which an inner circumference circle through which an end portion of the vehicle moving along the first circumference passes is separated from the avoidance circle. a route determination unit that determines a route from an initial position of a vehicle to a target parking position at a time of assisting the vehicle to be parked in a parking area, wherein the route determination unit includes, a first generation unit that generates a first circumference which is tangent to a straight line passing though the initial position and extending along a forward direction of the vehicle, and a second generation unit that generates a second circumference having a tangent line which is a line passing through a rear position of the vehicle positioned at a rear direction of the target parking position in the forward direction of the vehicle and extending along the forward direction of the vehicle, and having a radius as a turning radius at the time of minimum turning of the vehicle, wherein a part of the first circumference functions as a part of the route, and a part of a third circumference resulting from moving the second circumference along the forward direction of the vehicle functions as the route subsequent to the first circumference, and the second generation unit generates the third circumference resulting from moving the second circumference until an avoidance circle having a center at a corner portion of an obstacle disposed in the front direction of the parking area and having a radius as a predetermined distance and an outer circumference circle through which an end portion of the vehicle moving along the third circumference passes, become tangent to each other, characterized in that the first generation unit regenerates the first circumference which is tangent to the third circumference and generates the first circumference in which an inner circumference circle through which an end portion of the vehicle moving along the first circumference passes is separated from the avoidance circle.