To provide a modulation estimate processing method that solves a problem that disables a modulation estimate processing depending on the level of a received signal.

L.P.F processing sections 21, 22, threshold value decision processing sections 23, 24 and output control processing sections 25, 26 are newly added to a configuration realizing a conventional modulation estimate processing method. The threshold value decision processing section 23 outputs a primary signal received from a low-pass filter processing section 21 to the output control processing sections 25, 26 and compares levels of all samples of the primary signal with a threshold value and outputs a control signal to instruct an output of the received primary signal to a differentiation method part when there is no primary signal whose level is lower than the threshold value to the output control processing sections 25, 26. Furthermore, when there is any signal whose level is lower than the threshold value in the primary signals, the threshold value decision processing section 23 outputs a control signal to instruct an output of the received primary signal to a multiplication method part to the output control processing sections 25, 26.