Disclosed is a monitoring technique for displaying a low-luminance image of e.g. a dark area in an easily visible manner. The inventive apparatus includes an image capturing unit 10 for capturing an image of an object to be monitored, an inversion condition determining unit 11 for determining whether an inversion condition is satisfied or not based on the visibility of the image captured by the image capturing unit 10, and a display image generating unit 12 for generating a negative/positive inverted image from the captured image when it is determined by the inversion condition determining unit 11 that the inversion condition is satisfied.