An image recording apparatus is designed to decrease the size of an exposure unit, thereby allowing the exposure unit to move within a narrow space between an original document and a photosensitive material, to facilitate color adjustment and density adjustment, to provide a high resolution at low costs, and to prevent light fogging. The exposure unit is moved between a stage and a document table which hold a photosensitive material and an original document, respectively, so as to copy the image of the original document onto the photosensitive material by scanning exposure. An LED light source comprises three groups of light emitting elements which respectively emit blue, green and red colors, and a light beam from the LED light source is irradiated such that the light beam extends in a direction parallel to the original document and perpendicular to the direction of movement of the exposure unit (the forward and backward direction of the stage). The irradiated light is reflected by the original document and is caused to reach to a slit-like area of the photosensitive material through a SELFOC lens for exposure. Further, a mask member is moved together with the exposure unit so as to provide a light shield on both sides off the exposure unit in the direction of movement thereof, thereby preventing light fogging.