The present invention has a theme of a mobile body capable of suppressing rapid acceleration along a downward slope at a time of start. The mobile body comprises a driving force generation device which generates a driving force of the mobile body; a power accumulation device capable of supplying a power to the driving force generation device; a fuel cell capable of supplying a power to the driving force generation device; and a control device which controls driving of the driving force generation device. The control device prohibits to start driving the driving force generation device by the power supply of the power accumulation device in a case where the mobile body is positioned on a downward slope when starting the mobile body.