A fuel cell comprising: a power generation unit cooling passage configured to cool a power generation unit , which generates electricity by reacting hydrogen and oxygen, by circulation of a first heat medium; a radiator flow passage , which allows a second heat medium to flow through a radiator and circulate; a first circulation pump provided at the power generation unit cooling passage ; a second circulation pump provided at the radiator flow passage ; a heat exchanger configured to perform heat exchange between the first heat medium and the second heat medium; a first temperature detector configured to detect temperature of the first heat medium on an inlet side of the power generation unit ; and a second temperature detector configured to detect temperature of the first heat medium on an outlet side of the power generation unit , wherein the fuel cell is constructed in a manner such that output of the first circulation pump or the second circulation pump is controlled on the basis of temperature detected by the first temperature detector or the second temperature detector and a flow rate of the second heat medium to be sent out from the second circulation pump is decreased if the temperature of the first heat medium detected by the second temperature detector is equal to or lower than a predetermined value, characterized by further comprising a fan configured to cool the radiator , perform ventilation of a housing of the cell body , and dilute and discharge hydrogen if hydrogen leaks, wherein the fuel cell further comprises a hydrogen sensor configured to detect leakage of hydrogen, wherein the fuel cell is configured that the fan continues rotating and the first circulation pump and the second circulation pump stop if the hydrogen sensor detects leakage of hydrogen. a power generation unit cooling passage configured to cool a power generation unit , which generates electricity by reacting hydrogen and oxygen, by circulation of a first heat medium; a radiator flow passage , which allows a second heat medium to flow through a radiator and circulate; a first circulation pump provided at the power generation unit cooling passage ; a second circulation pump provided at the radiator flow passage ; a heat exchanger configured to perform heat exchange between the first heat medium and the second heat medium; a first temperature detector configured to detect temperature of the first heat medium on an inlet side of the power generation unit ; and a second temperature detector configured to detect temperature of the first heat medium on an outlet side of the power generation unit , wherein the fuel cell is constructed in a manner such that output of the first circulation pump or the second circulation pump is controlled on the basis of temperature detected by the first temperature detector or the second temperature detector and a flow rate of the second heat medium to be sent out from the second circulation pump is decreased if the temperature of the first heat medium detected by the second temperature detector is equal to or lower than a predetermined value, characterized by further comprising a fan configured to cool the radiator , perform ventilation of a housing of the cell body , and dilute and discharge hydrogen if hydrogen leaks, <EOS>