To perform the self-diagnosis of a three-axis acceleration sensor without making complex an electrode pattern.

A timer 19 switches a switch 18 and connects a counter electrode 17 to an oscillator 20. The oscillator 20 applies a DC voltage that changes at a specific frequency between the counter electrode 17 and an X-axis direction detection electrode 12, a Y-axis direction detection electrode 13, and a Z-axis direction detection electrode 14, thus vibrating a piezoelectric ceramic 11 and causing a self-generated polarization electric charge at each detection electrode. Each self-generated polarization electric charge is converted to X-direction voltage, Y-direction voltage, and Z-direction voltage by resistors 161-163 and amplifiers 151-153, and the direction voltages are compared with a reference voltage by comparators 231-233. When each direction voltage is smaller than the reference voltage, a logic value '1' that indicates the generation of a failure is outputted from an NAND circuit 22 and a failure detection signal is outputted from an AND circuit 21.