A living body state estimation apparatus acquires information indicating a state of a living body. The living body state estimation apparatus is configured to include an electrocardiogram signal acquisition unit which acquires an electrocardiogram signal of the living body and an information acquisition unit which acquires a parameter as the information, the parameter specifying a predetermined function indicating a probability distribution for a reference wave interval which is a time interval between peaks of consecutive predetermined reference waves in the acquired electrocardiogram signal.
