A chuck jaw changer for a machine tool has a jaw changing arm which is swingable about a vertical rotating shaft. The two ends of the arm have elongated magazine holders extending transversely to the length of the arm. The magazine holder has a guide groove in which an elongated jaw magazine is fitted slidably along the length of the holder. The magazine is formed with a plurality of jaw storage grooves spaced apart from each other and chuck jaws are detachably accommodated in the storage grooves, respectively. When the jaw changing arm is indexed to position the magazine holder into registry with the jaw mounting groove of the chuck, one of the jaw storage grooves of the magazine is brought into alignment with the jaw mounting groove so that a jaw changing device operates to shift the jaw between the storage groove and the jaw mounting groove for changing the jaw. The other jaw storage grooves can be brought into alignment with the jaw mounting groove one by one by shifting the magazine along the magazine holder by means of a traversing device.