A semiconductor package is provided with a package main body including a base portion configured by joining thin plates integrally, and a semiconductor device accommodating portion provided on one surface of the base portion, electric terminals electrically connected to a semiconductor device in the accommodating portion and exposed to an outer surface of the accommodating portion, and a heat high-transfer element including at least one layer-like member provided in the base portion. The layer-like member is configured independent of the base portion by a material having a thermal conductivity higher than that of the base portion, and extends from a position corresponding to a heat-generation site of the semiconductor device to a position in an outside of the heat-generation site corresponding position.