A machine tool is provided with a tool magazine including a guiding plate, a turntable and holders. The guiding plate includes an annular groove with a semi-circular section and a semi-oval section. The semi-circular section is defined by a radius. The semi-oval section is defined by a semi-major axis identical to the radius of the semi-circular section and a semi-minor axis shorter than the semi-major axis. The turntable includes claws extending from the periphery. Each of the holders is pivotally connected to a related one of the claws and includes an end for holding a tool and another end formed with a ball movably located in the annular groove. Thus, some of the holders of which the balls are located in the semi-circular section of the annular groove close while the other holders of which the balls are located in the semi-oval section of the annular groove open.