To surely eliminate the impurity of an oceanic life and the like when using, for example, sea water as a coolant by providing a heating fluid supply device for supplying a heated fluid at either one of the coolant side and or a side where the coolant is supplied of a plate-type heat exchanger.

For example, each one side of three plate-type heat exchangers 1a-1c has coolant supply pipes 2a-2c for guiding a coolant and a coolant return pipe for guiding the coolant after heat exchange to a drain pipe. When a microbe or oceanic life in the coolant are adhered in this king of coolant system, a heated fluid wire a relatively high temperature from a collection tank 7 being controlled to a proper temperature by an adjustment valve 12 being supplied to a side where the coolant is supplied of, for example, the heat exchanger 1c as a spare heats the heat-transfer element of the heat exchanger 1c and causes, for example, oceanic life being adhered to the coolant supply side to become extinct. Also, after, for example, the oceanic life of the heat exchanger 1c is eliminated, other heat exchangers 1a and 1b are also executed.