An electronic fence system comprises a fence wire which radiates a radio signal for defining a boundary; a transmitter electrically connected to the fence wire and transmitting a boundary radio signal including a mode selection signal; and a receiver attached to the pet, which receives the boundary defining signal with respect to a pet's approach to the fence wire, and which, depending on receiving the shock mode, applies an electrical shock only to the pet depending on receiving the shock mode, or depending on the shock after vibration mode which indicates a mode giving a shock after vibration, after vibration or vibration with a sound, applies an electrical shock to the pet if the boundary defining signal is continuously received or does not apply an electrical shock to the pet if the boundary defining signal is not received. If the pet has a hearing loss, or the circumference is noisy, a warning signal can be given through a touch to the skin of the pet. Since a vibration is applied first, and the shock follows it, no severe shock need be applied to the pet that will return into the confined area after having received a vibration. A pet's activity is restricted in a predetermined area.