To provide a machine for working metal plates with which the change of specification in company with stroke change or the like in a metal plate feeding mechanism is easily performed.

The machine includes frames 31, a working head 6 for performing working such as punching or laser beam machining to the metal plate W and the metal plate feeding mechanism 11 for feeding the metal plate W in a working position P with the working head 6. In the metal plate feeding mechanism 11, the metal plate W is fed in the metal plate feeding direction approaching and separating from the working position P by being guided with guide rails 18 supported on the frames 31. The frame 31 is composed of the frame main body 31A and an extended frame part 31B which is attached freely attachably and detachably to one end in the metal plate feeding direction of the frame main body 31A. The guide rail 18 is provided over the frame main body 31A and the extended frame part 31B.