A machine tool including a non-contact affected layer detection sensor capable of detecting an affected layer with high precision is provided. A machine tool includes a non-contact affected layer detection sensor, a main body, probes and that contact the surface of an workpiece, arm portions supported by the main body, and dimension measurement sensors that output a signal that corresponds to the dimension of the workpiece on the basis of displacement of the arm portions with respect to the main body. The affected layer detection sensor is provided in the arm portion, and outputs a signal that corresponds to an affected state of the workpiece. The arm portions hold the probes respectively, and are displaceable with respect to the main body in accordance with the dimension of the workpiece.