PURPOSE: To reduce an output value error of a strain gauge as caused by an unbalanced load.

CONSTITUTION: A sensing section 21 having a strain gauge 26a is provided at the portion of a pair of thin deformation parts 27 formed on a strain body 25 and a fixed support end 29 to which a fixing end 23 of the sensing section 21 is linked is connected to a mobile support end 30 to which a load receiving end 24 is linked with a pair of beams 31. A roberval mechanism part 22 in which a pair of beam upper thin deformation parts 32 is provided separately on the beams 31 to form a roberval mechanism is arranged and a separation distance between thin deformation parts 27 of the sensing section 21 is made to match that between beam upper thin deformation parts 32 of the roberval mechanism part 22. Thus, positional deviation values coincide in the direction orthogonal to the direction of loads generated on the sensing section 21 and the roberval mechanism section 22 to make the relationship linear between a load value and an output value of the strain gauge 26a thereby reducing errors in the output value of the strain gauge 26a.