A cutting fluid control device for a machine tool is used to adjust the amounts of supply of a cutting fluid and water, thereby controlling the concentration of the cutting fluid in a cutting fluid tank, and comprises an operating unit which inputs a machining condition of the machine tool, a computing unit which calculates the concentration of the cutting fluid based on the machining condition input through the operating unit, and an adjustment unit which adjusts the amounts of supply from a cutting fluid undiluted-solution supply device and a water supply device so that the concentration of the cutting fluid in the cutting fluid tank is equal to the cutting fluid concentration calculated by the computing unit.