PURPOSE: To provide a machine tool equipped with a feed amount sensing mechanism which can sense the feed amount from the rotational displacement irrespective of the configuration of a drive force transmission system for a feed shaft.

CONSTITUTION: A feed amount sensing mechanism 1 of a machine tool is composed as the fundamental configuration with a feed shaft 4 in the form of a piston rod of a hydraulic cylinder mechanism 3, a screw shaft 5 which is supported so that it is rotatable round the axis toward the feed shaft 4 and makes linear motions in the same direction and the same feed amount as the feed shaft 4, a ball screw nut 6 which is fixed on the body 2 side of machine tool and gives a rotational displacement amount corresponding to the screw shaft 5 linear motion amount to the shaft 5, with the displacement being generated round the axis L5 of the shaft 5, and an encoder 7 which senses the rotational displacement amount of the shaft 5.