A biosignal processing apparatus includes a signal acquisition unit and a determination unit. The signal acquisition unit is configured to acquire an output signal of an electrode that is placed on a biological surface. The determination unit is connected to the signal acquisition unit to determine, based on first frequency characteristics being frequency characteristics of the output signal, whether the electrode is in a first state in which the electrode is electrically connected to a measurement site of the biological surface or in a second state in which the electrode is electrically disconnected to the measurement site.
