To provide a step change device of a punching press unit which is capable of easily performing the punch-positioning even when the size and the punching position of a workpiece to be pressed are changed, and usable even in a space-saving manner.

The step change device of the punching press unit comprises: a punching press unit 2 having a frame 22 in which a frame upper part 22a with a punch 21 installed thereon and a frame lower part 22b with a die 23 installed thereon being opposite to each other; a cylinder-fitting bracket 7 with a driving piston type cylinder 4 connected to the punch 21 being fixed thereto; a robot arm fitting bracket 8 for connecting the cylinder-fitting bracket 7 with the driving piston type cylinder 4 being fixed thereto to a robot arm 5a; and a supporting pin moving mechanism 3 for connecting the punching press unit 2 and the robot arm fitting bracket 8 by fitting a supporting pin 31 movably attached to the robot arm fitting bracket 8 to a hole 32 formed in the frame upper part 22a.