To simply the configuration of equipment by accurately positioning sheet material even if a cutout for positioning the sheet material is not provided and an electric control circuit for detecting the edges of the sheet material is not installed.

A circular hole 20D is provided in a plate feeding guide 20, a fan 98 is installed on the rear side of the plate feeding guide 20, and the fan 98 is driven to feed air to the circular hole 20D. The air forms an air layer between a printing plate 12 and a plate feeding guide 20 when the printing plate 12 is placed on the plate feeding guide 20. By the air layer, the printing plate 12 reduces a frictional force in sliding for positioning on the plate feeding guide 20. Thus the positioning can be performed smoothly.