PURPOSE: To detect change in posture in many directions by making up each posture sensor of a first beam section formed in a structure liable to be strained so as to be deformed in a specified direction, and of a plurality of beams liable to be strained so as to be deformed in the direction different from that of the first beam, and making comparison strain signals from these detecting sections are made to pass through each low-pass filter.

CONSTITUTION: The quantity of displacement of each beam 102 and 104 is changed by that static force due to gravity is applied to the first and second beams 102 and 104 to change sensors in direction. When the beam section 102 is subjected to gravity in the direction 109, it is strained the most, and when the beam section 104 is subjected to gravity in the direction 110, it is strained the most. The quantity of strain in the beam section 102 is determined by its detecting sections 108 at both the sides of a neutral surface of strain, and the quantity of strain in the beam section 104 is determined by detecting change in capacitance between an electrode provided for a surface opposite to a second overlapping section 103 and the overlapping section 103. The voltage signal of the detecting section 108 and the capacitance signal of the beam section 104 are changed into voltage by a capacity-voltage conversion circuit 302, and the high frequency portion is cut-off by low-pass filters 303 and 305. Comparison is made by a comparison circuits 303 and 304 with voltage values set in advance, and judgement is made on the directions 109 and 110, so that a posture is thereby judged by a comparison circuit 307.