PURPOSE: To provide sampling synchronism which is stable against the local partiality of the absolute values of M series signals between a transmission side and a reception side as to the privacy communication device which uses the echo canceler.

CONSTITUTION: The DC component of the correlation signal between the same M series signals which are added on the transmission side and the signal generated by digitally converting a received privacy signal and the DC component of the correlation signal between the signal generated by delaying the M series signals by a constant time and the digitally converted signal are extracted by a loop filter 15 from their difference signal, and inputted to a DPLL 14 which determines a sampling frequency by adding the signal, generated by weighting the signal obtained by flattening the signals of the DC components through an integrator 18 through a multiplier 19, and the signal generated by weighting the signals of the DC components by a multiplier. Thus, the sampling frequency which drives an analog-digital converting circuit 13 is determined.