To provide an adaptive filter which insures stable convergence even to extreme fluctuation of a path having a plurality of responding parts defined as estimation objects and to a signal having relatively strong autocorrelation and intense strength and weakness changes such as a sound signal and which has a small hardware scale, a short convergence time and also a small amount of arithmetic operations.

This filter is provided with a storage circuit for storing the total amount of individual filter coefficient powers and positional information, a decision circuit for deciding a block that is made ineffective from an effective state according to the information from the storage circuit, a shift register applying queue processing to the positional information of the block decided as ineffective, and a control circuit for generating a control signal for controlling the connection of a matrix switch from positional information located at the top of the shift register and a filter number selected by the decision circuit.