In an echo canceller including an ADF and a cancellation adder, an ACANC calculator finds an average value of the amount of echo cancellation for a predetermined period to update the average value of the amount of echo cancellation, and detects a convergence state of the ADF to find the amount of echo cancellation in the convergence state of the ADF. A coefficient selector, when receiving a detection signal of the convergence state from the ACANC calculator, finds a power ratio of the sum total of power of all tap coefficients and the partial total of power of tap coefficients not to be assigned to taps to determine the effective number of taps useful for suppressing an echo component on the basis of the amount of echo cancellation and the power ratio. The ADF updates only the effective number of taps to disable the remaining taps.