A parking assistance device comprising: a route determination unit that determines a route from an initial position of a vehicle to a target 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 has a turning radius at the time of a minimum turning of the vehicle as a radius, and is tangent to a straight line passing through the target position and extending along the forward direction of the vehicle, characterized by: a second generation unit that generates a second circumference which is tangent to a straight line passing through the initial position and extending along a forward direction of the vehicle and is tangent to the first circumference, and a recalculation determination unit that generates a third circumference having a center at the position on an obstacle disposed in the front direction of the vehicle nearest to the route at the time of parking the vehicle and having a predetermined radius, and determines whether or not the recalculation of the route is necessary based on the first circumference and the third circumference, wherein a part of the first circumference functions as a part of the route, and wherein a part of the second circumference functions as a part of the route subsequent to the part of the first circumference. a route determination unit that determines a route from an initial position of a vehicle to a target 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 has a turning radius at the time of a minimum turning of the vehicle as a radius, and is tangent to a straight line passing through the target position and extending along the forward direction of the vehicle, characterized by: a second generation unit that generates a second circumference which is tangent to a straight line passing through the initial position and extending along a forward direction of the vehicle and is tangent to the first circumference, and a recalculation determination unit that generates a third circumference having a center at the position on an obstacle disposed in the front direction of the vehicle nearest to the route at the time of parking the vehicle and having a predetermined radius, and determines whether or not the recalculation of the route is necessary based on the first circumference and the third circumference, a first generation unit that generates a first circumference which has a turning radius at the time of a minimum turning of the vehicle as a radius, and is tangent to a straight line passing through the target position and extending along the forward direction of the vehicle, characterized by: a second generation unit that generates a second circumference which is tangent to a straight line passing through the initial position and extending along a forward direction of the vehicle and is tangent to the first circumference, and a recalculation determination unit that generates a third circumference having a center at the position on an obstacle disposed in the front direction of the vehicle nearest to the route at the time of parking the vehicle and having a predetermined radius, and determines whether or not the recalculation of the route is necessary based on the first circumference and the third circumference, a second generation unit that generates a second circumference which is tangent to a straight line passing through the initial position and extending along a forward direction of the vehicle and is tangent to the first circumference, and a recalculation determination unit that generates a third circumference having a center at the position on an obstacle disposed in the front direction of the vehicle nearest to the route at the time of parking the vehicle and having a predetermined radius, and determines whether or not the recalculation of the route is necessary based on the first circumference and the third circumference, wherein a part of the first circumference functions as a part of the route, and wherein a part of the second circumference functions as a part of the route subsequent to the part of the first circumference.