A numerically controlled machine tool is disclosed including a spindle support structure for moving the spindle having a tool mounted thereon in directions along an X-axis, a Y-axis and a Z-axis, a workpiece support structure having an indexing workpiece mounting table, and a chip discharge means located between the spindle support structure and the workpiece support structure for discharging chips produced in the machining area to the outside. Since the workpiece mounting table is allowed for rotational indexing, the setup process for the workpiece can be performed with the workpiece mounting surface of the workpiece mounting table facing upward, and therefore the setup process can be shortened while at the same time improving the machine operating rate. Also, since the spindle support structure, the workpiece support structure and the chip discharge means can be configured separately from each other, the machine tool can be manufactured and installed easily.