Abstract: A pressure sensor includes: a pressure conversion unit and a signal processing circuit installed in a semiconductor substrate. The pressure conversion unit includes: a diaphragm formed by partially thinning the semiconductor substrate; and a plurality of piezo resistive elements formed on a surface of the diaphragm. The signal processing circuit is constituted by a complementary metal-oxide semiconductor (CMOS) integrated circuit formed in a p-type conductive region disposed around the diaphragm on the surface of the semiconductor substrate, and the piezo resistive elements are provided by forming an n-type conductive region in the p-type conductive region on the surface of the diaphragm by diffusion of n-type impurities and diffusing p-type impurities in the n-type conductive region.