A biological signal processing apparatus includes: a provider which provides state probability which corresponds to a value of a first biological signal； an acquirer which acquires a first biological signal in time series from a living body and which acquires state probability in time series which corresponds to a value of the acquired first biological signal from the provider； and a determiner which acquires determination probability based on the state probability acquired by the acquirer and which performs determination whether a process is performed or not by using the determination probability.
