To provide an impression cylinder pressing apparatus and a method for roughly adjusting longitudinal registering capable of finishing rough adjustment of the longitudinal registering in a short time, and making its work simple and decreasing the burden.

In a longitudinal registering roughly adjusting mode, a control is performed in such a way that an air pressure at a vent opening becomes an air pressure canceling its own weight of an impression cylinder by a vent opening air pressure controlling means, and the control is performed in such a way that an air pressure at a feed opening becomes the atmospheric pressure by a feed opening air pressure controlling means. Namely, the own weight of the impression cylinder is canceled and no printing pressure is loaded to make a web wound on the impression cylinder free, and a tension is quickly unified and the position of the impression cylinder is kept at a feed position as it is.