An ebullient cooling device, comprising: an engine coolant passage configured to be formed inside an internal combustion engine; a gas-liquid separator for separating a coolant that is discharged from the engine coolant passage into a liquid-phase coolant and a gas-phase coolant; a condenser for returning the gas-phase coolant that is separated at the gas-liquid separator to a liquid-phase coolant; a first passage that connects the condenser and the engine coolant passage; a second passage that branches from the first passage at a connection portion being a location partway along the first passage, and is connected to the gas-liquid separator; a first water pump that is provided between the connection portion and the engine coolant passage, and that is configured to feed a liquid-phase coolant from the first passage to the engine coolant passage during operation of the internal combustion engine; a second water pump that is provided between the connection portion and the condenser; actual temperature measurement means that is provided in the second passage, or in the first passage between the connection portion and the engine coolant passage, and configured to be used for measuring an actual temperature of a liquid-phase coolant; the ebullient cooling device being characterized by further comprising: boiling temperature calculation means for calculating a boiling temperature of a liquid-phase coolant that is fed from the first water pump to the engine coolant passage based on a pressure of a gas-phase coolant in the gas-liquid separator; and coolant feeding means configured to drive, in a case where the actual temperature is higher than the boiling temperature, the second water pump to feed a liquid-phase coolant from the condenser to the first water pump whereas not driving the second water pump in a case where the actual temperature is lower than the boiling temperature. an engine coolant passage configured to be formed inside an internal combustion engine; a gas-liquid separator for separating a coolant that is discharged from the engine coolant passage into a liquid-phase coolant and a gas-phase coolant; a condenser for returning the gas-phase coolant that is separated at the gas-liquid separator to a liquid-phase coolant; a first passage that connects the condenser and the engine coolant passage; a second passage that branches from the first passage at a connection portion being a location partway along the first passage, and is connected to the gas-liquid separator; a first water pump that is provided between the connection portion and the engine coolant passage, and that is configured to feed a liquid-phase coolant from the first passage to the engine coolant passage during operation of the internal combustion engine; a second water pump that is provided between the connection portion and the condenser; actual temperature measurement means that is provided in the second passage, or in the first passage between the connection portion and the engine coolant passage, and configured to be used for measuring an actual temperature of a liquid-phase coolant; the ebullient cooling device being characterized by further comprising: boiling temperature calculation means for calculating a boiling temperature of a liquid-phase coolant that is fed from the first water pump to the engine coolant passage based on a pressure of a gas-phase coolant in the gas-liquid separator; and coolant feeding means configured to drive, in a case where the actual temperature is higher than the boiling temperature, the second water pump to feed a liquid-phase coolant from the condenser to the first water pump whereas not driving the second water pump in a case where the actual temperature is lower than the boiling temperature. boiling temperature calculation means for calculating a boiling temperature of a liquid-phase coolant that is fed from the first water pump to the engine coolant passage based on a pressure of a gas-phase coolant in the gas-liquid separator; and coolant feeding means configured to drive, in a case where the actual temperature is higher than the boiling temperature, the second water pump to feed a liquid-phase coolant from the condenser to the first water pump whereas not driving the second water pump in a case where the actual temperature is lower than the boiling temperature.