Abstract: To provide an insert part weld molding method for reliably welding an insert part to a blow molded object while preventing an unwelded portion from being created at a circumferential edge of the insert part in a thickness direction thereof. An insert part weld molding method welds a blow molded object to an insert part 3 set in a mold 7, wherein a molding surface 7a of the mold 7 is set higher than a front surface 6d of a portion to be welded of the insert part 3, and an entire surface of a circumferential edge 6b of the insert part 3 in the thickness direction thereof and a parison 11 of the blow molded object are brought into a gapless welded state.

Abstract: To provide an insert part weld molding method for reliably welding an insert part to a blow molded object while preventing an unwelded portion from being created at a circumferential edge of the insert part in a thickness direction thereof. An insert part weld molding method welds a blow molded object to an insert part 3 set in a mold 7. wherein a molding surface 7a of the mold 7 is set higher than a front surface 6d of a portion to be welded of the insert part 3, and an entire surface of a circumferential edge 6b of the insert part 3 in the thickness direction thereof and a parison 11 of the blow molded object are brought into a gapless welded state.