A linear drive unit and a machine tool having the linear drive unit, capable of being applied to various applications, while taking into consideration the balance between the thrust force and the cogging of a linear motor. The linear drive unit has a magnetic gap changing mechanism which is configured to change a magnitude of a magnetic gap between a coil and a magnet, by displacing at least one of the coil and the magnet so that the coil and the magnet approach or are separated from each other.