PURPOSE: To facilitate the conveyance and positioning of press plate in a short time and contrive to shorten the press plate conveying and processing time by a method wherein a press plate conveying device for feeding press plate to a developing device is equipped with a press plate positioning means for widthwise positioning the press plate during the conveyance of the press plate.

CONSTITUTION: A crossfeeding conveyor 16, which conveys a press plate delivered from two composers as the printing devices of a press plate processing line to the right and left direction (X-direction), consists of a X-direction conveying part 25, on which the press plate delivered from a second composer provided on the right side of the device concerned, and a junction part 26, which locates on the left of the device concerned and is arranged between the first and the second composers. In the above-mentioned crossfeeding conveyor 16, at the junction part 26, a X-direction positioning device 29, a crossfeeding device 36, which consists of some part of a second conveying device, and a widthwise shifting device 32 are equipped. The widthwise shifting device 32 consists of two rollers 66 for feeding the press plate to Y-direction and a positioning mechanism 67 including widthwise shifting pins shiftable to the axial direction of the roller 66.