PURPOSE: To prevent an adverse effect to an image by setting the distance from an image exposing part to a nearest conveying means in front, shorter than the dimension in the conveying direction of a film sheet while longer than the dimension in the conveying direction of an effective image area formed on said film sheet.

CONSTITUTION: A film sheet conveying mechanism consisting of a conveying guide 15, a conveying guide plate 17 which is projected from an automatic exposing unit 20, and a pair of conveying rollers 21, is provided in front of an image exposing part, in a film-sheet conveying mechanism in which the conveying speed of the pair of conveying rollers 21 is lower than the sheet conveying speed at an image exposing part. In this case, a distance L from the contact point between a sub-scanning drum 8 and a rear-stage nip roller 9 to the contact point between the pair of conveying rollers 21 is set shorter than the dimension in the conveying direction of a film sheet S while longer than the distance in the conveying direction of an effective image area formed on the film sheet S. Accordingly, even if an error occurred in conveyance at the exposing part, the image is not affected.