A display system of electronic manual which allows easy identification of wirings. The display system of electronic manual is provided with a storage device in which stored is an electronic manual provided with a wiring diagram described in a vector image description language and constituted so as to allow reading by a browser program. In response to user's selection of a component on the wiring diagram displayed on a display, a wiring display system highlights the selected component. In response to user's operation of selecting the highlight, the wiring display system highlights wirings extending from the selected component. Moreover, while the wiring is highlighted, in response to user's operation of selecting gray display, the wiring display system switches the elements other than the selected component and the wirings extending from the component on the wiring diagram displayed on the display to be displayed in weak gray.