PURPOSE: To obtain a product having superior vibration-proof property by a method wherein terminal grooves opened at the collar of the spool of an electromagnetic coil formed by thermo-plastic resin are provided and a terminal having broader width than the width of the terminal grooves and irregularity at both sides are heated and pressed in the terminal grooves.

CONSTITUTION: A plurality of terminal grooves 5 are provided at the collar section 1a of the spool 1 of an electromagnetic coil formed by thermo-plastic resin. The width 7 of a coil terminal 4b is slightly broadened than that 6 of the terminal grooves and notches 4d are provided at both side section of the tip of the terminal. The tip 4c of the terminal is previously heated or the tip 4c of the terminal is superimposed on the terminal grooves 5 and is heated, pressed and inserted in the terminal grooves 5 by applying supersonic wave vibration. Or the tip 4c of the terminal is pressed and inserted in the terminal grooves 5 before hardening immediately after the molding of the spool. This permits terminal connection causing no looseness by vibration.