An image forming apparatus comprises: a photoreceptor drum (8); an LED head (10) for exposure provided along the width of the photoreceptor drum (8); a pin (19,20) provided on the LED head (10); a supporting base substance to which the photoreceptor drum (8) is attached; and a pin admitting groove (37,38) provided on the supporting base substance for admitting the pin. The LED head (10) is half-fixed on the supporting base substance. <IMAGE>
