A disclosed mobile body includes an energy generator configured to generate energy from a supplied fuel gas; a gas leakage detecting unit configured to detect leakage of the fuel gas out of the energy generator; a control unit configured to control power output of the energy generator; an information obtaining unit configured to obtain environmental information on an environment around the mobile body from a predetermined information source; and a power-control-manner determining unit configured to determine a power-control manner, in which the control unit controls the power output of the energy generator, based on the environmental information on the environment around the mobile body when leakage of the fuel gas is detected by the gas leakage detecting unit.