To variably change the filter characteristic of a decimation filter in accordance with a sampling rate. A decimation filter 13 in a semiconductor device 1 sequentially inputs a signal sampled at a predetermined sampling rate fos, and calculates, for each input signal that is input within a predetermined period (a period for M+2N), a filter coefficient Cj for performing predetermined filtering processing in response to a trigger signal TR continuously applied, and furthermore sequentially multiplies the input signal by the calculated filter coefficient, accumulates a multiplication value within the predetermined period, and sequentially outputs the result. The predetermined period is made variable in accordance with a time interval at which the trigger signal is applied.