The invention provides a machine tool capable of facilitating a switching between a guide bush mode and a non-guide bush mode. A machine tool comprises a headstock provided with a main spindle for gripping a workpiece, a rail extended along a main spindle axis, a first bearing fixed to the headstock and guided on the rail, a second bearing fixed to the headstock on the front side of the first bearing and guided on the rail, a supporting bed on which a guide bush is removably mounted, and a guide mounted on the supporting bed to movably support the headstock in a direction of the main spindle axis when the guide bush is removed. The rail provides a larger play on the second bearing when the headstock is supported by the guide than when the headstock is not supported by the guide.