1. An image pickup apparatus for outputting image data on an image for which image processing is executed to a computer, said image pickup apparatus comprising: a thermal image capturing camera for capturing a thermal image; a visible-light camera for capturing an image under a visible light; a temperature zone extracting portion for detecting and extracting a portion corresponding to a predetermined temperature zone given from an outside from the thermal image; a background image extracting portion for extracting an image of an immobile object in the image captured under the visible light by said visible-light camera as a background image; and a synthesizing/outputting portion for synthesizing the portion extracted by said temperature zone extracting portion, and the background image extracted by said background image extracting portion with each other, and outputting image data on a resulting synthetic image.