When a vehicle body is on board an escalator, a control device (100) makes an ejection determination by use of an external sensor (4). The control device (100) makes an ejection determination by use of front-wheel rotation sensors (6). The control device (100) makes an ejection determination by use of an inclination detecting unit (118). The control device (100) switches a control mode from a boarding control mode to an ejection control mode, when at least one of the above three ejection determinations is affirmatively made.