Abstract: The present invention relates to a machine tool system and a machining liquid supply device for machining a workpiece by a tool such as a grinding wheel or a milling cutter, and solves the problem of how to supply the machining liquid optimally to an area where the tool engages with the workpiece. In order to solve this problem, the present invention is so configured that during the machining of a workpiece with a tool (T) detachably mounted on a spindle (12) of a machine tool (MT), the machining liquid supply device (18) for supplying a machining liquid to a machining area of the tool (T) is provided with an opening end at the forward end of a machining liquid supply nozzle (20), and can give the movements in a radial direction and a circumferential direction through 360° with respect to the axis of the spindle (12) about the spindle head (12) having the spindle (12) through a rotational supporting body (16) by means of linear movement means (80) and rotating movement means (30), respectively.