A digital camera 800 receives from lighting units 120a-120l lights temporarily changing in luminance and produces a coordinates data list 8031 of the lighting units. Decoding unit 804 reads change in luminance at each luminance-point coordinates of the lighting unit to decode information. It is judged based on the decoded information of a data format 900, whether plural luminance-point coordinates having the same guidance point ID information 902 are found. When the plural luminance-point coordinates having the same guidance point ID information are found, a location of the plural luminance-point coordinates is analyzed to draw and display a circumscribed polygon having its vertices at these coordinates on a through image in an overlapping manner. A hatched area is set inside the circumscribed polygon and the decoded information is displayed within the hatched area.