To excellently perform automatic monitoring using a picked-up image.

When an image is picked up using a zoom lens which is variable in angle of field of imaging, a moving body is detected from an image signal obtained by imaging (step S11). A motion vector showing a movement quantity per unit time of the moving body detected through the moving body detection processing is detected (step S13) and compared with a reference value (step S15). On the basis of the comparison result, a field angle set value of the zoom lens is adjusted (steps S16, S17).