To provide a safety door so constructed that a work is put in and out without fully opening the safety door, and when the safety door of a machine tool is opened, a cooling liquid drop adhering to the safety door will not dirt the work floor.

This safety door of a machine tool is fitted to the machine tool for machining a tool with a tool to be opened like a single swing door or laterally slid. A small door 8 formed by a transparent plate and capable of moving up and down is provided on the lower part or the central part of the safety door 1 in a position for taking out or providing a work, and in a position below the small door, a trough 7 inclined at an angle of 1 to 10 degrees to the horizontal direction is provided extending from the right frame 6c to the left frame 6d on a lower frame 6a of the frame of the safety door.