A video controller generates a video signal from image data on the basis of a print instruction, and an engine controller controls a laser scanner in accordance with the generated video signal to record an image on recording paper by an image forming section. A master controller of an optional master unit performs overall control of a variety of optional units, such as a paper-deck optional unit and a sorter optional unit, in dependence upon a control instruction sent from the video controller. Accordingly, it is possible to provide an image recording apparatus to which a wide variety of optional units can be connected freely without raising the cost of the main body of the apparatus.