A processing device according to an embodiment includes a sound pickup signal acquisition unit that acquires sound pickup signals picked up by left and right microphones through a monophonic input terminal, a switch unit that switches a connection state so that a first sound pickup signal picked up only by the left microphone and a second sound pickup signal picked up only by the right microphone are input, an interaural distance acquisition unit that acquires an interaural distance of the listener, a front time difference acquisition unit that acquires a front time difference, an incident time difference calculation unit that calculates an incident time difference based on an angle θ, the front time difference, and the interaural distance, and a transfer characteristics generation unit that calculates transfer characteristics by applying a delay corresponding to the incident time difference to the first and second sound pickup signals.