To provide a method for manufacturing a coil assembly 26 of an electromagnetic valve 3 wherein the periphery of a winding composed of a solenoid coil 4, a terminal 5 and a coil bobbin 6 is coated with a secondary resin mold member 7, thereby preventing the seal property of a liquid seal such as fuel or oil from being degraded, and preventing an insulation property from being degraded.

At a secondary forming step of the coil assembly 26, front ends of a plurality of projections 53 formed in the collar-shaped part 52 of the coil bobbin 6 are plugged into a plurality of recesses 71 of a second resin forming die 8 for forming a secondary mold, so that the built-in winding can be positioned so as not to move by forming pressure at the secondary forming step. Therefore, a secondary resin mold member 7 can be resin-molded at a uniform thickness on the entire periphery of an insert product (the solenoid coil 4, the terminal 5 and the coil bobbin 6).