A bridge circuit includes four gage resistors. Each gage resistor is divided into two division gage resistors. A couple of division gage resistors. The junction points between division gage resistors outputting the same potential when no pressure is applied are used for diagnostic. Four gage resistors out of the eight gage resistors are arranged near the center of diaphragm 14, and the other four division resistors are arranged near the peripheral edge portion of the diaphragm 14 to make the stress distribution even.