An image processor for a robot system, performing image processing for a video signal output from a camera. The camera can output a first video signal including obtained image data as well as internal vertical and horizontal synchronization signals, and output a second video signal including image data obtained based on external vertical and horizontal synchronization signals as well as the external vertical and horizontal synchronization signals. The image processor includes a synchronization signal separation section separating the internal horizontal synchronization signal from the first video signal output from the camera; a synchronization frequency detection section detecting a frequency of the separated internal horizontal synchronization signal; an external synchronization signal generation section generating the external vertical and horizontal synchronization signals; and a processing section allowing, at desired timing, the external synchronization signal generation section to generate the external vertical synchronization signal, to generate the external horizontal synchronization signal at the detected frequency of the internal horizontal synchronization signal, and to supply the generated external vertical and horizontal synchronization signals to the camera.