A parking space detection apparatus detects a parking space of an own vehicle and includes: a vehicle determination section that determines whether an other vehicle is present on at least one of two sides of a parking space, based on search information acquired from an in-vehicle search section that searches for the parking space; a width calculation section that, it is determined that the other vehicle is present on at least one of the two sides of the parking space, calculate a width of the parking space on an entrance side and a width of the parking space on an inner side based on the search information; and a parking determination section that determines whether the own vehicle is able to park in the parking space based on the widths of the parking space on the entrance side and on the inner side and size of the own vehicle.