The present invention discloses an apparatus of cardiopulmonary resuscitator that is operated through a driving mechanism controlled and driven by air power. The driving mechanism functions to actuate a belt adapted to extend around the chest of a patient to generate reciprocating movement of pressing and releasing so as to achieve a purpose of cardiopulmonary resuscitation for recovering heartbeat and breathing of the patent. By means of the disclosure of the present invention, the apparatus of cardiopulmonary resuscitator is capable of being operated in any kinds of occasions without worrying about lack of power electricity. Meanwhile, the driving mechanism can provide higher reliability and lower cost through the mechanism design that is more simplified than the design of electrical control element used in the conventional apparatus.