Intertial sensor

An inertial sensor comprising a sensing portion having a weight (12) hung by beams (13) extending from a frame (14), the weight being a movable portion. The beams include distortion portions partially arranged therein, and the distortion portions are arranged to avoid edges on which stresses applied to the beams are concentrated. Roots of the beams (R) are not formed at right angle in connecting to the weights or the frame. The roots of the beams have wider angles. It is thus possible to dissipate areas on which stresses are concentrated and improve the impact resistance without sacrificing the sensor sensitivity. Both high sensor sensitivity and the impact resistance are obtainable in accordance with the present invention.