Abstract: There is provided a machine tool apparatus provided with coolant supply passages for supplying a coolant in tools or tool mounts for mounting the tools. An oil coated water droplet generator/mixer is connected to the beginning end of the coolant supply passages, and a spray port having a smaller inner diameter than that of the coolant supply passages is connected to the termination end of the coolant supply passages such that the oil coated water droplets generated in an atomized state by the oil coated droplet generator/mixer flow in a liquid state through a coolant supply passages while having a droplet shape on a surface of which in the greater part of oil coated water droplets an oil film is formed and are sprayed again in an atmized state from the spray port.