PROBLEM TO BE SOLVED: To easily confirm the present state of an object to be observed on site by only photographing the object to be observed or its vicinity without performing particular operation.SOLUTION: When an object to be observed (plant) or its vicinity is photographed by an imaging part 15, a mobile terminal device 1 receives and acquires an observation result of the object to be observed in its photographed image (monitor image) from an observation device 2 on the plant side, reads out and acquires state expression information representing the present state of the object to be observed from a character table T3 according to the acquired observation result, and displays the state expression information on a display 16 in association with the object to be observed in the photographed image.
