A sound signal processing device that acquires a collected-sound signal obtained by sampling a sound collected by a microphone at a first sampling frequency, and receives a reproduced-sound signal obtained by sampling a sound for reproduction at a second sampling frequency different from the first sampling frequency, and then converts the sampling frequency of the reproduced-sound signal into the first sampling frequency so as to remove an acoustic echo from the collected-sound signal by using the reproduced-sound signal whose sampling frequency has been converted.