An electronic device includes a cover module and a host having a lighting unit. The cover module has a light permeable cover, a system signal indicator, and a transmission unit. The cover has an outer surface, an opposite inner surface, and a fixing structure extended from the inner surface. The system signal indicator has a transparent portion having a plurality of indicating icons and an opaque portion. The transmission unit is fixed on the fixing structure, and the system signal indicator is sandwiched between the transmission unit and the inner surface. The cover module is installed on the host, and the transmission unit is aligned with the lighting unit. Thus, the transmission unit is used for transmitting light, emitted from the lighting unit, to the outer surface via the system signal indicator and the inner surface in turn, for showing the indicating icons on the outer surface.