PURPOSE: To obtain a resin sealing method for positively setting a lead frame in a mold without a positional shift even if the lead frame is thermally expanded with respect to a method for sealing a semiconductor element mounted on a lead frame with a resin.

CONSTITUTION: In this method, a lead frame 13 with an element 15 mounted thereon is provided between upper and lower molds 1, 7 respectively provided with cavities 2, 9, and a resin is charged into the cavities 2, 9. The lead frame 13 is placed on the lower mold with the upper and lower molds 1, 7 opened so that a positioning hole 14 provided in the lead frame 13 is opposed to a positioning pin 18 provided on the lower mold 7. An expandable ejector pin 4 is provided on the upper mold so as to protrude to the vicinity of the positioning hole 14 of the lead frame 13.