The cutting fluid supply device of a machine tool includes a storage tank of a cutting fluid, a cutting fluid discharge port which discharges the cutting fluid, at least one pump which feeds the cutting fluid to the cutting fluid discharge port, a first filter, a second filter which has filter performance different from the first filter, a path switching unit which switches the paths of the cutting fluid and a control unit, and the control unit controls the pump and the path switching unit so as to switch, as the paths, to a first path along which the cutting fluid is fed without being passed through the filters, a second path along which the cutting fluid is passed through the first filter and is fed and a third path along which the cutting fluid is passed through the second filter and is fed.