To more easily retrieve a necessary moving image and to more properly express a situation when trouble occurs, in a display device 14 connected to an external device 1, taking in state data corresponding to a control state by the external device 1, and performing unit screen display corresponding to a change of the state data on a display screen 26.

The state data are recorded in synchronism with moving image data 50 taken in from an image pickup means 42 to allow reproduction, and the state data are used as a keyword to indirectly retrieve the moving image data. Display of the state data displayed in the same time as the moving image is expressed as a change of a figure such as a graph or a unit screen.