Abstract: An intrusion alarming apparatus according to this invention detects the human body present in a sensing zone thereof and sends out warning information by means of sound and light. Detection of the human body depends on a human body sensor which emits detection signals in response to variation in the strength of heat rays or interception of radiated infrared rays. Information by the use of sound and light is effected by driving a sound-using alarm such as a speaker and a light-using alarm such as a stroboscope with a sound emission driving circuit and a light emission driving circuit which operate on the basis of detection signals output by the human body sensor. The driving circuits for sound and light emission are connected to each other so as to be operated by means of a single timer circuit.