Rochelle salt gives rise resonance lines which are called piezoelectric lines in the wide range of 550 MHz from 3 MHz. In a previous paper, temperature dependence of these lines was reported and it was revealed that in Rochelle salt the temperature coefficients defined by (1/v)(dv/dT) was about -12 × <10>^<-4> at room temperature. The purpose of the present experiment was to investigate properties of the piezoelectric lines and to derive suggestions on mechanism of the resonance from these.