An information providing system includes a sound emission device for emitting, as sound wave, identification information modulated into a sound signal, an identification information resolution server including a mapping table in which the identification information, valid time information and the address information of a content are stored to be associated, and a mobile terminal device for transmitting the identification information demodulated from a picked-up sound wave to the identification information resolution server thereby obtaining address information and accessing the content using the obtained address information. When received the identification information from the mobile terminal device, the identification information resolution server returns the address information of a corresponding content to the mobile terminal device when the time information is within a valid time.