A slope having a main plate for changing position between a low position and a high position, and a control unit for controlling position change of the slope, are included. The control unit includes: a first mounting detection means which detects a state of being mounted or a state of not being mounted by a wheelchair with regard to the main plate; a second mounting detection means which detects a state of being mounted or a state of not being mounted by a wheelchair with regard to a ground side plate; a third mounting detection means which detects a state of being mounted or a state of not being mounted by a wheelchair with regard to a vehicle side plate; and a ground detection means which detects whether the end of the ground side plate at the rear side of a vehicle is in contact with a ground surface.