An ultrasonic-wave communication system which performs communication using ultrasonic waves between a plurality of beacons which emits ultrasonic waves and a portable terminal, wherein: each beacon is configured to be able to emit three or more signal carriers predetermined as frequencies different from each other, to output a data signal formed by the three or more signal carriers according to predetermined information, and to emit a dummy signal to supplement changes in sound pressure during outputting the data signal so that the sound pressure output from each beacon is within a predetermined range; and the portable terminal includes: a microphone; a demodulation processing unit which performs demodulation processing to demodulate the three or more signal carriers by analyzing frequencies or wavelengths of ultrasonic waves sent from the beacon upon receiving the ultrasonic waves; and a decryption processing unit which performs decryption processing to decrypt the predetermined information based on the data signal recognized by the demodulation processing; wherein: a combination of the three or more signal carriers is individually assigned to each beacon (5A, 5B) with frequency settings being different from each other, and each beacon (5A, 5B) generates beacon information of one channel based on the assigned combination and sends out the beacon information as an ultrasonic wave; and the demodulation processing unit of the portable terminal receives the beacon information suitable for frequency characteristics of the microphone among the beacon information of the ultrasonic wave sent from the respective beacons (5A, 5B) and performs demodulation processing for the received beacon information. each beacon is configured to be able to emit three or more signal carriers predetermined as frequencies different from each other, to output a data signal formed by the three or more signal carriers according to predetermined information, and to emit a dummy signal to supplement changes in sound pressure during outputting the data signal so that the sound pressure output from each beacon is within a predetermined range; and the portable terminal includes: a microphone; a demodulation processing unit which performs demodulation processing to demodulate the three or more signal carriers by analyzing frequencies or wavelengths of ultrasonic waves sent from the beacon upon receiving the ultrasonic waves; and a decryption processing unit which performs decryption processing to decrypt the predetermined information based on the data signal recognized by the demodulation processing; a combination of the three or more signal carriers is individually assigned to each beacon (5A, 5B) with frequency settings being different from each other, and each beacon (5A, 5B) generates beacon information of one channel based on the assigned combination and sends out the beacon information as an ultrasonic wave; and the demodulation processing unit of the portable terminal receives the beacon information suitable for frequency characteristics of the microphone among the beacon information of the ultrasonic wave sent from the respective beacons (5A, 5B) and performs demodulation processing for the received beacon information.