The image forming apparatus includes a video controller unit that receives image information to convert the image information into an image signal for image formation, an engine controller unit that controls image formation, a laser driver unit that emits a laser beam, and a plurality of signal lines that connect the video controller unit, the engine controller unit, and the laser driver unit to each other, wherein the laser driver unit detects the laser beam emitted from the illumination element and generates a horizontal synchronization signal which is electrically transmitted via any one of the plurality of signal lines and used as the reference of an image writing timing in response to the detection. Among the signal lines, a signal line for transmitting the image signal or a control signal electrically and a signal line for electrically transmitting the horizontal synchronization signal are used as a common signal line.