sensor section 68 in the width direction further the sensor section 68 is fitted to the sensor supporting member 69 in such a manner that the surface of opposite side to the surface opposite to the linear scale 66 of the sensor section 68 is brought into contact with the second positioning member 70 and when the sensor section 68 is rotated along the peripheral surface of the second positioning member 70 around this contact position the fitting position is adjusted so that the opposite surface to linear scale 66 of the sensor section 68 is parallel to the linear scale 66 hereupon it is structured in such a manner that according to the detection result of the encoder the operation of linear motor is controlled and the laser light irradiation device 59 is conveyed so that the scanning of laser light by the laser light irradiation device 59 is accurately conducted on the downstream side of the conveying path from the supporting drum 54 a peeling device 71 to peel the recording medium 51 which is exposed by the laser light irradiation device 59 into the first sheet and the second sheet is provided and lower the delivery tray 57 a collecting roller 72 by which the first sheet peeled from the second sheet by the peeling device 71 is wound and collected is provided further on the downstream side of the conveying path from the peeling device 71 a delivery roller 73 to deliver the second sheet in which the image is formed to the delivery tray 57.