PURPOSE: To suppress change in the temperature of fluid by cooling or heating the fluid through sensing of the fluid temp. on the upper flow side of an electromagnetic pump as well as to relieve the variation of fluid pressure through use of a pressure relieving device.

CONSTITUTION: A thermosensor 7 is provided at a piping 6 on the upper flow side of an electromagnetic pump 3, and the fluid temp. sensed is converted into a control signal at a temp. control device 8 to control a heater 10, a damper 12 and a blower 12, which constitute a cooling and heating arrangement. Thus the temperature change of the fluid can be suppressed. Accordingly the fluid flowing into the electromagnetic pump 3 has a temperature equal to or near the set temp., so that the rate of flow can be controlled constant without changing the voltage impressed on the pump 3 to a great extent. For pressure change of the fluid, on the other hand, a pressure relieving device 14 is used to relieve changes of the pressure on the upper flow side of pump 3.