A sensor includes detecting element (28) with an acceleration sensor, which is formed of weight (18) coupled to rigid section (14) via flexible section (16), substrate (10) confronting weight(18), and an electrode section including opposed electrodes (20, 22, 24, 26) placed on respective opposed faces of weight(18) and substrate (10). This structure prevents weight (18) from moving along Z-axis, so that a detection accuracy of acceleration occurring along X-axis or Y-axis can be improved.