To obtain the maximum lubrication effect by the minimum fluid injection by fluid jetting an incombustible gas from the chip discharge side.

An incombustible gas such as nitrogen gas, carbon dioxide, etc., is supplied into a plurality of nozzles 10 mounted on a main spindle 3 through each opening and closing valve V1, V2, V3, V4 which are normally closed from a supply source 20. The optimum pressure suitable for a workpiece and a tool T is supplied in a scope of about 1 to 20 kg/cm2. Moreover, its jet temperature is adjusted to an adequate temperature in a scope of formal temperature to about 150°C below zero. When a side face of the workpiece is machined in this condition, the incombustible gas is jetted in fluid from the chip discharge side for a machining point of the tool T which cuts the workpiece due to the rotation of the main spindle 3. That is, the opening and closing valve V2 of the nozzle positioned at a machining point on the cut-in side of the tool T for the workpiece is opened and operated based on a command for opening which is programmed in advance.