A hearing aid comprising: a receiver configured to convert an electric signal into sound; a microphone configured to convert sound into an electric signal; an adaptive filter configured to adaptively estimate a feedback transfer function (F(z)) from the receiver to the microphone; a subtractor configured to subtract an output signal of the adaptive filter from an output signal of the microphone, thereby generating a first signal (e(n)); a hearing aid processor configured to perform predetermined hearing aid processing for the first signal (e(n)), thereby generating a second signal (s(n)) to be input to the receiver; a first whitening filter configured to whiten the first signal (e(n)); a second whitening filter having a whitening filter coefficient (γ(n)) identical to that of the first whitening filter and configured to whiten the second signal (s(n)); a coefficient updater configured to update a coefficient (W(n)) of the adaptive filter based on each of output signals of the first and second whitening filters (15, 16); and a controller configured to perform control of operation of the adaptive filter and the first and second whitening filters (15, 16), wherein the controller calculates an average (ψ(n)) of the whitening filter coefficients (y(n)), and updates and saves, as a stabilization coefficient (Ws(n)), when it is, as a result of comparison between a preset first threshold and the average (ψ(n)), determined that the average (ψ(n)) is smaller, determines a presence or absence of a change in the feedback transfer function (F(z)) based on the coefficient (W(n)) of the adaptive filter and the stabilization coefficient (Ws(n)), and performs, when it is determined that the feedback transfer function (F(z)) has changed, the control in order that effectiveness of whitening by the first and second whitening filters (15, 16) is reduced as compared to that when it is determined that the feedback transfer function (F(z)) does not change. a receiver configured to convert an electric signal into sound; a microphone configured to convert sound into an electric signal; an adaptive filter configured to adaptively estimate a feedback transfer function (F(z)) from the receiver to the microphone; a subtractor configured to subtract an output signal of the adaptive filter from an output signal of the microphone, thereby generating a first signal (e(n)); a hearing aid processor configured to perform predetermined hearing aid processing for the first signal (e(n)), thereby generating a second signal (s(n)) to be input to the receiver; a first whitening filter configured to whiten the first signal (e(n)); a second whitening filter having a whitening filter coefficient (γ(n)) identical to that of the first whitening filter and configured to whiten the second signal (s(n)); a coefficient updater configured to update a coefficient (W(n)) of the adaptive filter based on each of output signals of the first and second whitening filters (15, 16); and a controller configured to perform control of operation of the adaptive filter and the first and second whitening filters (15, 16), wherein the controller calculates an average (ψ(n)) of the whitening filter coefficients (y(n)), and updates and saves, as a stabilization coefficient (Ws(n)), when it is, as a result of comparison between a preset first threshold and the average (ψ(n)), determined that the average (ψ(n)) is smaller, determines a presence or absence of a change in the feedback transfer function (F(z)) based on the coefficient (W(n)) of the adaptive filter and the stabilization coefficient (Ws(n)), and performs, when it is determined that the feedback transfer function (F(z)) has changed, the control in order that effectiveness of whitening by the first and second whitening filters (15, 16) is reduced as compared to that when it is determined that the feedback transfer function (F(z)) does not change. determines a presence or absence of a change in the feedback transfer function (F(z)) based on the coefficient (W(n)) of the adaptive filter and the stabilization coefficient (Ws(n)), and performs, when it is determined that the feedback transfer function (F(z)) has changed, the control in order that effectiveness of whitening by the first and second whitening filters (15, 16) is reduced as compared to that when it is determined that the feedback transfer function (F(z)) does not change.