To desirably decrease the number of components of a communication system, used for small-sized electronic equipment, so as to facilitate the electronic equipment main body small-sized and lower the cost secondarily and to lower the power consumption of small-sized portable equipment to realize long-time operation by a battery power source.

The communication system has on its transmission side a data modulating means 1, a piezoelectric element driving means 2 which is connected to the voltage output of the data modulating means 1, and the piezoelectric element 3 which is driven by the piezoelectric element driving means 2 and on its reception side a piezoelectric element and a data demodulating means 6 which inputs a voltage from the piezoelectric element, propagates the pressure vibration generated by the piezoelectric element 3 having received the voltage output of the modulating means 1 of the transmission-side system to the piezoelectric element of the reception-side system through a transmission medium which can propagate the pressure vibration or a vibration transmission part 14 which efficiently transmits a frequency component used to communicate the piezoelectric element vibration to the transmission medium, and converts the vibration into a voltage signal by the piezoelectric element of the reception-side system and demodulates it.