To provide a press plate attaching/detaching apparatus capable of simply attaching/detaching the press plate by a simple structure.

A long hole having an opening which is elongated in an axial direction of a plate cylinder 1, a tension bar 16 having a hook part fitted in the long hole, an opening and closing lever 12 pivoting the tension bar 16 between a closed position and an open position, a lever swinger 26 swinging the opening and closing lever which is non rotary to a rotary center of a plate cylinder and swings the opening and closing lever by engaging an engaging part, and a press plate presser 13 which presses a holding rear of the press plate into the opening part. The opening and closing lever 12 has an arcuate surface positioning almost concentrically to an outer peripheral surface of the plate cylinder 1 when the tension bar 16 exists at an open position. When a holding hip part is pushed into the opening part, an engaging part of the lever swinging apparatus 26 is engaged with the arcuate surface to hold the tension bar 16 at an open position. After pushing into the opening of the holding hip is completed, engagement with the arcuate surface of the engagement part is released and the tension bar 12 is composed to be pivoted to a closed position of the tension bar 12.