[Problem] To provide a sleep stage determination device that is able to make a high-accuracy determination of sleep stage using a proper normalization technique in conformity to international sleep depth determination criteria. [Solution] The sleep stage determination device according to the present invention is provided with: a normalization unit 6 that controls a peak value at a constant level by performing gain control with respect to a user's heartbeat signal detected non-invasively and without any restraints, and performs normalization on data of a heartbeat signal intensity calculated using the gain value at that time; and a sleep stage determination unit 8 that determines the user's sleep stage on the basis of a normalized heartbeat intensity normalized by the normalization unit 6 and a variance value which indicates variation in data over a predetermined time period and which is calculated with respect to the normalized heartbeat intensity data.
