An NC lathe with a robot for automatically exchanging works and chuck claws comprising a numerically controlled lathe having a rotatable chuck, a robot disposed in the vicinity of the numerically controlled lathe, and a feeder disposed in the vicinity of the robot. Groups of works and magazines containing chuck claws are placed on the pallets carried on the feeder, forming respective sets. The robot executes the exchanging operation of the works and the chuck claws between the feeder and the chuck.