To provide a method of manufacturing a sealed semiconductor that can mold sealed resin (precursor) into a desired shape relatively easily and demold the sealed semiconductor easily even when a mold release film is preheated at a low temperature region.

A method of manufacturing a sealed semiconductor includes a mold release film installation process, a sealed resin injection process, a semiconductor immersion process, and a sealed resin solidification process. In the mold release film installation process, a mold release film 200 having a cushion layer 220 whose main component is polyolefin is made to follow a recess (cavity) 310 of a mold 300. In the sealed resin injection process, sealed resin 400 is injected into a recess 311 (hereinafter, referred to as a "mould release recess"), which the mold release film is made to follow. In the semiconductor immersion process, a semiconductor 120 is immersed into the sealed resin in the mold release recess. In the sealed resin solidification process, sealed resin is solidified with the semiconductor being immersed in the mold resin.