two axes are perpendicular each other so that the rotation angular accelerations applied to each axis may not influence each other position guides 205 207 209 211 are formed in the four corners in which two plate arms intersect each other the cross shaped elastic plate 203 is fixed to the supporting frame 220 by inserting these position guides to guide grooves 221 223 225 227 a supporting step 229 is projected in a predetermined height from a supporting plate 230 so that the cross shaped elastic plate 203 may not contact the supporting plate 230 when the arms of the cross shaped elastic plate 203 vibrate since the other structures except above described are similar to the angular acceleration sensor shown in fig1 more detailed description will be abbreviated in another embodiment of the present invention a strain gage can be used in place of the piezoelectric element the strain gage can be formed of a conductive material in case that the strain gage changes lengthwise its resistance is proportional to the length and inversely proportional to the sectional area in case that the strain gages are attached onto the upper side of the elastic plate 106 as shown in fig3 a 3 c when the rotation force is applied in direction of 34 b 34 the left side strain gage 119 receives tensile forces which results in the increase of its length and the decrease of its cross sectional area thereby its resistance increases on the other hand the right strain gage 121 receives compressing forces which results in the decrease of length and the.