Disclosed is a method for producing a synthetic resin mold package at high yield from which package a pair of the surface of an internal device is exposed. A to-be-exposed part of the surface of the internal device composed of an insulating substrate (2) and thin film electrodes (4, 5) and an insulating protective film (6) formed on the substrate is covered with a coating agent (42), and a die pad portion (8) is bonded to the back surface of the internal device. After placing the thus-obtained structure in a mold consisting of a lower mold (46) and an upper mold (48), a pin (50) is inserted into the mold so that the front end of the pin is pressed against the die pad portion (8), thereby keeping the surface of the coating agent (42) pressed against the inner surface of the upper mold (48). Then, a synthetic resin (52) is injected into the mold and cured therein. The thus-obtained resin sealed body is taken out from the mold, and the coating agent (42) is removed from the resin sealed body.