Abstract: According to the present invention, there is provided a vertical machining center (1) which has working regions (&agr;, &bgr;) separable by a partition plate (P), and comprises a spindle head (15) adapted to move within one of the working regions (&agr;, &bgr;) separated by the partition plate (P) in a first machining mode and to move across the working regions (&agr;, &bgr;) not separate by the partition plate (P) in a second machining mode, and a stopper (20) which prevents the spindle head (15) from moving from the one working region into the other working region in the first machining mode and permits the spindle head (15) to move between the working regions (&agr;, &bgr;) in the second machining mode. The stopper (20) includes a movable stopper member (21) attached to a saddle (13) and stationary stopper members (26,27) attached to a bed (11).