PURPOSE: To make the detection of thrust accurate, by providing supporting beams having the same length, at the both ends of the inside of a pair of parallel beams, which have rigid cross sections and the same length, or at the intermediate part between both ends thereof so that those beams intersect at right angles, and attaching strain gages to the beams.

CONSTITUTION: A parallelogram load cell 10 is composed of upper and lower parallel beams 12' and 12", which are rigid, long in the right and left directions, and are not deformed, and supporting beams 14, 16 and 18. Sais supporting beams support the respective upper and lower parallel beams 12' and 12" in parallel at two points at front and rear ends 14 and 16 of the parallel beams or at the equi-distant dividing point between said two points. Holes along the longitudinal axes of the parallel beams are formed at the intermediate parts between the upper and lower sides in the supporting beams. The cross section is reduced along the parallel beam axes, and shearing- stress concentrated, flexible cross sections 20' and 20" are formed. Shearing-force detecting, intersected surfaces 22', 22", 24', and 24" are attached to one or more of the supporting beams. The displacement of the parallel beams 12' and 12" due to the shearing force detection or the thrust along the parallel axes that are the cause of the displacement is detected. Thus the thrust can be accurately detected.