A main scale graduation, an auxiliary scale graduation or the like provided in a conventional micrometer is omitted, and a thimble 71 is provided at a regular position in the axial direction of the spindle 61 through a sleeve 51 in a frame 1 to rotate about the axis of a spindle 61. Between the thimble 71 and the spindle 61, a rotation transfer means 81 for transferring the rotation of the thimble 71 to the spindle 61 and allowing the spindle 61 to displace in the axial direction of the spindle 61. As the rotation transfer means 81, a ratchet system 82 is used.