The objective of the present invention is to provide accurate position data of a cellular phone utilizing illuminative light based radio communication. In FIG. 1, an emergency light or guided light (illuminating device) (10) on for 24 hours, for example, emits a visible light (illuminative light) modulated based on information of its position. A cellular phone (20) having a visible light receiving unit (a camera, for example) may obtain position data by receiving and demodulating that visible light. When conducting emergency communication (emergency telephone number 110 or 119) with the obtained position data, the position data may be automatically added for data communication in addition to the information by voice.