An insert molding method includes holding a plurality of insert members in a molding die to be separated from one another, and subsequently filling a resin into the molding die to fill a gap between the insert members and a periphery thereof with the resin to form an insert molded product such that the insert members are separated at a preset interval from one another. The molding die includes a space-maintaining projection for maintaining a separation interval between the insert members at the preset interval or more, the projection being formed on an inner wall surface of the molding die opposite to a longitudinal end of the insert members, and a gate for filling the resin therethrough into the molding die, the gate being formed on an inner wall surface of the molding die opposite to a side of the insert members in a width direction thereof.