An analog-state video signal is inputted from each of several in-vehicle cameras via a corresponding signal cable. An amendment amount for making uniform signal levels of the analog-state video signals originating from the respective in-vehicle cameras is determined, with respect to each of the analog-state video signals, based on a burst signal included in each analog-state video signal. According to the determined amendment amounts, the analog-state video signals are amplified to make uniform the signal levels, obtaining analog-state uniformed video signals, respectively. A composite image of combining images originating from the in-vehicle cameras is generated based on the obtained analog-state uniformed video signals.