A device for adjusting eccentric value at an eccentric portion of crank shaft in press machine having: a main portion at the crank shaft rotatably supported by a frame; an eccentric portion having an axis eccentric from that of the main portion and adapted to be coupled into a connecting member of the press machine, the main portion and the eccentric portion being capable of leaving from each other along the axis of the crank shaft; connecting means provided at a connecting portion where the main portion and the eccentric portion contact with each other for connecting the main portion with the eccentric portion so that eccentric value of the eccentric portion from the main portion can be altered; and drive means for moving the connecting means.