PURPOSE: To obtain an energy-saving pump, by driving a reciprocating pump by use of a heat-sensitive power source having an actuating rod which is moved reciprocally in response to temperature change.

CONSTITUTION: As the atmospheric temperature is raised, a heat-sensitive medium 4 is expanded in response to the temperature rise, and an actuator rod 7 is moved to the left by the pressure caused by expansion of the heat-sensitive medium 4. This causes a rocker arm 14 to turn in the same direction, so that a cam plate 3 is turned in a clockwise direction by a one-way clutch 13. Resultantly, a pump actuating rod 25 is raised upward by a power transmitting plate 31, and a diaphragm 24 is deflected upward. With resultant opening of an intake valve 27 and closing of a discharge valve 29, fluid is drawn into a pump chamber A from an intake pipe 28. Thus, it is enabled to obtain a pump of the type capable of saving energy.