Abstract: Provided are a coolant supply device and a machine tool in which ejection of a coolant is easily switched on and off. A coolant supply device 10 for supplying a coolant to a workpiece machining area in a machine tool, the coolant supply device comprising: a rotary nozzle 40 formed to have a cylindrical shape and having, at an outer circumferential face thereof having the cylindrical shape, an ejection port 51 for ejecting the coolant; and a supply device body 20 rotatably supporting the rotary nozzle and configured to be capable of supplying the coolant to the rotary nozzle. The supply device body is configured to be capable of switching an ejection allowed range in which the ejection port is opened and an ejection stopped range in which the ejection port is blocked from each other in accordance with rotation of the rotary nozzle.