A cutting method in which a solution is sprayed or jetted to a machining portion when machining by use of a water-insoluble cutting oil, wherein recovered liquid is collected and stored in one recovery tank, and separated into the water-insoluble cutting oil and another solution on the basis of the specific gravity difference, and are re-used. Stable machining is enabled by using the water-insoluble cutting oil, and measures against disaster are fully taken.