Abstract: In a displacement measuring instrument comprising a main scale secured to a first member, and an index scale secured to a second member and reciprocatingly movable together with this second member along the main scale whereby a relative movement between the first and the second members is measured from a relative movement between the main and the index scales, there are provided a highly rigid member rotatably engaged at one end thereof with the second member and at the other end thereof with the index scale whereby the second member and the index scale are connected to each other, and a biasing means loaded between the second member and the highly rigid member for urging the index scale against the main scale.