To prevent the feeling of incompatibility in an image processing process from being applied to a person watching a main monitor by inhibiting the update of conversion contents of image signals stored in a preview memory through input inhibition setting and converting images in preview and main memories to the same conversion contents based on input inhibition setting.

The image signals of image picked-up object are stored in a preview memory 6 and a main memory 14, and the image is processed by converting digital image data from the memory 6 through a look-up table converter 8a by a D/A converter 8 for preview output and outputted through a preview output terminal 10 to a preview monitor 40. When a main image update switch 20 is in an update inhibited state, the input of digital image data to a memory 14 for main output is inhibited by a control part 12 and when the switch 20 is in an update permitted state, the input of digital image data to the memory 14 for main output is permitted. Therefore, no image effect is not propagated on the main monitor during image processing on the preview monitor.