A machine tool comprising: a stationary bed; a workpiece support unit to support a workpiece; a tool support unit to support a tool, the workpiece support unit and the tool support unit being mounted on the stationary bed for selective advance and retraction relative to each other in a direction parallel to a cutting direction; a drive mechanism to selectively advance and retract the workpiece support unit and the tool support unit relative to each other; and a displacement measuring unit to measure a displacement (ΔL) of a workpiece center-to-blade tip distance, which is a distance in the cutting direction between a center equivalent position (Xw) of the workpiece support unit and a blade tip equivalent position (Xt) of the tool support unit; therein the displacement measuring unit is provided on a continuous path between the center equivalent position (Xw) of the workpiece support unit and the blade tip equivalent position (Xt), which path avoids a processing movement region in which the workpiece and the tool undergo a relative movement, and measures the displacement (ΔL) of the workpiece center-to-blade tip distance by measuring the displacement of the continuous path, and a linear position detecting unit (31, 32) including a scale (31a, 32a) extending in a direction parallel to the cutting direction and a readout head (31b, 32b) to read the scale (31a, 32a) is provided characterized in that the displacement measuring unit comprises: a reference frame, which is made of a thermal expansion material having a lower coefficient of thermal expansion than that of the stationary bed and is disposed on the stationary bed having been positioned on the continuous path; and that one of the scale (31a, 32a) and readout head (31b, 32b) being provided in the reference frame. a stationary bed; a workpiece support unit to support a workpiece; a tool support unit to support a tool, the workpiece support unit and the tool support unit being mounted on the stationary bed for selective advance and retraction relative to each other in a direction parallel to a cutting direction; a drive mechanism to selectively advance and retract the workpiece support unit and the tool support unit relative to each other; and a displacement measuring unit to measure a displacement (ΔL) of a workpiece center-to-blade tip distance, which is a distance in the cutting direction between a center equivalent position (Xw) of the workpiece support unit and a blade tip equivalent position (Xt) of the tool support unit; therein the displacement measuring unit is provided on a continuous path between the center equivalent position (Xw) of the workpiece support unit and the blade tip equivalent position (Xt), which path avoids a processing movement region in which the workpiece and the tool undergo a relative movement, and measures the displacement (ΔL) of the workpiece center-to-blade tip distance by measuring the displacement of the continuous path, and a linear position detecting unit (31, 32) including a scale (31a, 32a) extending in a direction parallel to the cutting direction and a readout head (31b, 32b) to read the scale (31a, 32a) is provided characterized in that the displacement measuring unit comprises: a reference frame, which is made of a thermal expansion material having a lower coefficient of thermal expansion than that of the stationary bed and is disposed on the stationary bed having been positioned on the continuous path; and that one of the scale (31a, 32a) and readout head (31b, 32b) being provided in the reference frame.