Abstract: An apparatus for continuously measuring blood pressure of a subject based on magnitude variation of heartbeat-synchronous pulses produced from the subject, the apparatus including a detecting device for continuously detecting the pulses, the detecting device including an inflatable cuff to be set around a body portion of the subject, magnitude of the pulses being varied as pressure in the inflatable cuff is varied, the varying magnitude of the pulses being detected by the detecting device, a selecting device for selecting a pulse from the pulses detected at a preceding blood pressure measuring cycle, the selected pulse corresponding to maximum blood pressure determined at the preceding measuring cycle, a first determining device for determining a reference value based on at least a magnitude of the selected pulse, a second determining device for comparing, with the reference value, the varying magnitude of the heartbeat-synchronous pulses detected at a current blood pressure measuring cycle, and determining a