To provide a water spray type internal combustion engine having high thermal energy utilization efficiency while reducing the possibility of damaging the engine with water spray.

Only when receiving a detection signal from a cooling medium temperature sensor 8 showing that the temperature of cooling medium is a set temperature value or higher and receiving a detection signal from a pressure sensor 7 showing that maximum pressure in a combustion chamber is a set pressure value or higher, a control device 9 uses a water supply pump operation control signal to permit the water spray of a water supply pump 62. At other times, the control device 9 uses the water supply pump operation control signal to prohibit the water spray of the water supply pump 62. When using the water supply pump operation control signal to stop the water spray of the water supply pump 62, the control device 9 outputs a signal to an internal combustion engine main control device MCU to operate the internal combustion engine with no water spray over the following certain time.