A fuel cell and a temperature measurement method capable of directly measuring average temperature of a power generation unit and preventing dropout of a temperature detecting device are provided. A cathode plate for fixing the position of a power generation unit is set to be in contact with the power generation unit in a heat-transfer fashion and is made of an electric conductor or a semiconductor. When the temperature changes accompanying power generating operation of the power generation unit, the temperature of the cathode plate which is in contact with the power generation unit in a heat-transfer fashion changes. According to the temperature change, the resistance value changes. The resistance value is detected by using a resistance voltage dividing circuit having the cathode plate and resistors. By obtaining the temperature coefficient of the cathode plate in advance, the average temperature of the entire power generation unit is measured from the resistance value of the cathode plate.