PURPOSE: To prevent a crack of a coil insulation material from occurring, whose generative cause is in that the thermally expanded quantity of a coil conductor is larger than the one of the coil insulation material in the state of a high temperature.

CONSTITUTION: In an electromagnetic pump having in its casing a radial stator core and a ring-like coil 12, which are used in the environment of a high temperature, on the outside of a coil conductor 13 of the coil 12, provided is a circular ring 16 having a thermal expansion coefficient smaller than the coil conductor, and both the coil conductor and the circular ring having the small thermal expansion coefficient are covered with an insulation material 14.