The present disclosure relates to a parking assistance system for searching for a parking space and parking a vehicle in the parking space, which includes: a determinator configured to determine whether or not the vehicle is in a stopped state based on movement information of the vehicle; a calculator configured to calculate inclination information, which is an inclination of the vehicle or road surface on which the vehicle is located, using an inclination sensor included in the vehicle; a memory configured to store traveling information including first inclination information when the first inclination information calculated by the calculator is less than predetermined threshold inclination information in a parking space searching step, and configured to maintain the first inclination information or update the traveling information by changing the first inclination information into second inclination information based on at least one of a stopped time during which the vehicle remains stopped and the second inclination information measured during the stopped time in a parking step in which parking is processed; and a controller configured to control the vehicle to move toward the parking space based on the traveling information stored in the memory.