Abstract: The portable breathing apparatus according to the present invention includes an air tank chargeable with air at the predetermined pressure and portable, a pressure valve member bypassing one portion of air when the pressure of air supplied from the air tank falls less than certain pressure, a regulator valve member converting air induced from the pressure valve member into breathable pressure, thereby regularly supplying the converted air to a mouth, a pressure switching member enabling electric power to be switched on/off by compressed air, induced and bypassed from the pressure valve member, and a vibration means, contactable to a human body, generating vibration at the same time when the electric power of the pressure switching member is switched on, thereby warning lack of compressed air.