An apparatus for alerting a doctor which provides an alarm corresponding to a patient, and receives living body information signals transmitted through a transmitter. The apparatus alerts a doctor with a buzzer sound or a vibration indicating that the condition of the patient and of the living body information signals has changed suddenly. The apparatus includes a portable casing having a front plate, a rear plate, a top plate, a bottom plate, a left plate, and a right plate. The casing is provided with a circuit plate on which an electric circuit is mounted which receives and treats the living body information signals. Moreover, the apparatus is provided with a display portion provided on the casing and connected with the electric circuit. The wave form of at least an electrocardiogram signal included in the living body information signals is displayed on the display portion.