A heartbeat analyzer analyzes heartbeats of a living body to which a pacing device for outputting pacing pulses to cause a heart to beat is placed. The heartbeat analyzer includes: a heartbeat detecting section that detects the heartbeats； a pulse detecting section that detects outputs of the pacing pulses； a heartbeat determining section that determines whether the heartbeats are paced beats due to the pacing pulses or not, based on detection timings of the pacing pulses； a tachycardia determining section that, in a case where the paced beats are in a number that is equal to or larger than a predetermined heart rate, and are contained in the heartbeats at a predetermined ratio or more, determines that pacing tachycardia caused by the pacing pulses occurs in the living body； and a notifying section that notifies of the occurrence of the pacing tachycardia.
