To prevent the generation of warpages on a mold package at normal temperature times after molding at high temperature irrespective of sealing resin and the material of a lead frame, regardless of differing thermal expansion coefficients.

A resin sealing mold 10 has a surface with which an upper mold cavity block 18a and a lower mold cavity block 18b are pinched, and the upper surface and the lower surface of each cavity 16a have the curved surface having a prescribed curvature. As a result, a double-sided mold package is formed into a desired warped shape at high temperature in advance, the shape of desired warpage warped to the opposite direction, thereby being mutually canceled in the stage of shrinkage of thermosetting resin, having difference thermosetting coefficients and the lead frame process, the lead frame when the mold package returns to normal temperature state, and the double-sided mold package, having the upper and the lower flat surfaces in parallel with each other, can be obtained.