PURPOSE: To obtain an electromagnetic pump which has large capacity of pump function though small by providing a lubricant layer at the opposed face to the outer duct of an iron core block, or at the outer surface.

CONSTITUTION: Each iron core block 1, which is arranged around an outer duct 4 constituting one part of an annulus passage 3, is fastened with bolts 15 besides being inserted freely in a groove 17 having margin provided in a supporting member 12 which surrounds the outer duct 4, and the inner face contacts with the periphery of the outer duct 4 and is supported by it. Moreover, a lubricant layer, to which a molybdenum dioxide capable of withstanding high temperature is applied in film shape and which is not shown in the figure, is provided at the contact face between the iron core block 1 and the outer duct 4. Hereupon, when the iron core block 1, by the heat generation by the exciting means of a coil 2, and the outer duct 4, by the temperature of fluid, thermally expand, respectively, and contact with each other, even if the friction by the axial displacement of the outer duct occurs, the lubricant layer prevents the damage of the contact face.