To widen the measuring range of a strain measuring instrument so that the instrument can measure a large strain.

In a strain measuring instrument 10, a pair of fixtures 14 and 16 which are stuck to the surface 12 of a platy rubber material 12 at a prescribed interval is provided. One end sections of hooks 22 and 24 are respectively engaged with the through holes 18 and 20 of the erected parts 14B and 16B of the fixtures 14 and 16. The other end sections of the hooks 22 and 24 are respectively engaged with through holes 28 and 30 bored near both end sections of a rectangular gauge sticking plate 26. Strain gauges 32 are stuck to both the front and rear surfaces of the plate 26 while the phosphor bronze plate is bent.