PURPOSE: To transmit the heat produced in the stator of a motor through filling thermally-radiant resin material and radiate the heat through a resin case by a method wherein the resin case is filled with the thermally-radiant resin material having fluidity and a space between the stator and the resin case is filled with the thermally-radiant resin material.

CONSTITUTION: A cylindrical partition 8 and slot insertion members 9 are respectively made to protrude inside a resin case 6 so as to face the end surface of a stator 4 and the slot insertion members 9 are inserted into slots 10 and the tip parts of the partition 8 are pressed against the end surfaces of the stator 4 hermetically. One or a plurality of resin casting holes 11 and air vent holes 12 which are provided axis-symmetrically are drilled in the one side end surface of the resin case 6 and thermally-radiant resin material 13 is cast through the casting holes 11 to fill a space 14 between the stator 4 and the resin case 6 with the resin material 13. With this constitution, the heat produced in the stator 4 cab be transmitted to the resin case through the resin material and radiated, so that the temperature rise of the motor can be suppressed.