PURPOSE: To obtain a failure detection circuit of a semiconductor acceleration sensor which can positively detect failure by connecting the output of an acceleration signal to the ground positively when a beam part of the semiconductor acceleration sensor is damaged.

CONSTITUTION: In a semiconductor acceleration sensor, a semiconductor substrate is formed by supporting a movable part 2 at the center using a beam part 3 with elasticity for a surrounding support part 1 by etching, a strain gauge 4 is provided at the beam part 3, a bridge circuit 7 is formed by resistors R1 and R2 by utilizing the strain gauge 4, and then the output of the bridge circuit 7 is taken out as an acceleration signal through an amplification circuit. Then. the resistors R1 and R2 for compensating temperature are provided between the bridge circuit 7 and the amplification circuit, the resistors are connected to a comparator CO1 through diodes D1 and D2, and then the comparator CO1 is connected to the output side of the amplification circuit. thus abnormally increasing voltage at the input side of the amplification circuit by the provision of the resistors for compensating temperature when the beam part 3 is damaged and there is no signal from the bridge circuit 7 and forcing the output of the amplification circuit to be connected to the ground level by detection using the comparator CO1.