A parking assistance device includes: a route determination unit that determines a route from an initial position of a vehicle to a target parking position when assisting the vehicle to be parked in a parking area, and includes, a first generation unit generating a first circumference tangent to a line passing though the initial position and extending along a forward direction of the vehicle, and a second generation unit generating a second circumference having a tangent line passing through a rear position of the vehicle at a rear direction of the target parking position in the forward direction and extending along the forward direction, and having a radius of minimum turning of the vehicle, a part of the first circumference functions as a part of the route, and a part of a third circumference functions as the route subsequent to the first circumference.