An echo reducer includes: an obtainer configured to obtain frequency characteristics of a transmission system from a sound emitter of a sound emission and collection device to a sound collector of the sound emission and collection device; a determiner configured to determine whether or not both a transmission signal and a reception signal in the sound emission and collection device are in a state of including a sound; and an attenuator configured to attenuate the reception signal to be output to the sound emitter, by attenuation characteristics corresponding to the frequency characteristics of the transmission system that the obtainer obtains, when the determiner determines that both the transmission signal and the reception signal in the sound emission and collection device include a sound.