A digital filter includes: integration calculation units (10) that are cascade-connected, are fed time-division-multiplexed data, the time-division-multiplexed data being formed of pieces of data on M channels that are time-division multiplexed, the pieces of data on the respective channels being updated at a rate equal to a sampling frequency fs, operate in accordance with a clock having a frequency fs×M, and integrate the time-division-multiplexed data for every M samples; a frequency conversion unit (11) that operates in accordance with a clock having a frequency fD×M, decimates data at the sampling frequency fs input from the integration calculation unit (10) in the last stage at a sampling frequency fD, and delays data obtained as a result of decimation by (M−1) samples; and difference calculation units (12) that operate in accordance with the clock having the frequency fD×M, are cascade-connected to the output of the frequency conversion unit (11), and each subtract, from data input thereto, data M samples before.