Provided is a piezo-resistive pressure sensor that realizes sensitive and accurate measurement of pressure, by reducing the variation of electrical conduction due to thermal variation in piezo resistance elements, without lowering the sensitivity of measurement. Piezo-resistance sections R1, R2, R3 and R4 are arranged on diaphragm 31, near the border between diaphragm 31 and support section 32. By this means, pressure can be measured with high sensitivity. The area of a part where a group of piezo-resistance elements are placed, and the outer shape of that part, are the same between piezo-resistance sections R1, R2, R3 and R4. By this means, piezo-resistance sections R1, R2, R3 and R4 have uniform temperature distribution and reduce the variation of electrical conduction due to thermal variation in piezo resistance elements.