PURPOSE: To make it possible to change all chucks in one-time changing step, by rotatably providing a pawl storage ring in a chuck pawl changing device in a lathe, and by providing pawl changing mechanisms each composed of means for engaging and disengaging between pawls and chucks and means for transferring the chucks.

CONSTITUTION: A storage ring 16 capable of storing a plurality of pawls 12 to be changed is rotatably arranged around a chuck 5. Further, pawl changing mechanisms composed of means for engaging and disengaing between the pawls and the chuck 5, such as, for example, a release cylinder 23, a release lever 23a, etc. and means for transferring the pawls 12 between the storage ring 16 and the chuck 5, such as, for example, a shift cylinder 20, a shifter 21, an arm 22, etc., are provided in a number which is equal to the number of pawls 12 that may be set on the chuck 5. Accordingly, all the chuck 12 may be simultaneously changed so that the time necessary for changing the pawls 12 are remarkably reduced.