PURPOSE: To reduce the effects of torsion and bending and to improve detecting accuracy, by forming the second strain yielding parts, which are longer than the first strain yielding part, and attaching strain gages to the first strain yielding part.

CONSTITUTION: Screw holes of a material to be measured are coupled with through holes 12 and 12 by way of attaching bolts. Then a tensile load acts on both end parts of a strain yielding body 11. The rigidity of a part other than a first strain yielding part 14 and second strain yielding parts 15 and 16, which are longer than the part 14, is high. Therefore, strain is not yielded. The first and second strain yielding parts 14, 15 and 16 are elongated in the longitudinal direction (load applying direction) and contracted in the direction of the width (direction perpendicular to the load applying direction). Strain gages SG1 and 2 and strain gages SG3 and 4 are attached to the upper surface and the lower surface of the strain yielding part 14. The strain gages SG1W4 are deformed in correspondence with the elongation and contraction of the strain yielding part 14, and their resistance values are changed. The four strain gages SG1W4 form a bridge circuit. Therefore the bending and torsional outputs are cancelled. An electric signal corresponding to the strain of the strain yielding part 14 is taken out of the output terminals of the bridge. Thus the load value is measured. Since the strain yielding in the strain yielding part 14 is large, the strain detecting sensitivity is improved to the large extent.