Machine tool having a bed, a table arranged on the bed, a first saddle provided free to travel back and forth, a second saddle supported on the first saddle and provided free to travel side to side, a spindle head provided free to travel perpendicularly on the second saddle, a main spindle situated above the table and by the spindle head supported free to rotate on its center axis, a front cover provided on the front side of the bed and furnished with doors that open and close sideways, and top covers configured with one end sideways shiftably connected to the front side of the first saddle, and with another end connected extensibly/retractably to the top of the front-cover doors, therein being configured for permitting back-and-forth-directed movement of the first saddle.