An exoskeleton apparatus driven by a pneumatic artificial muscle with functions of upper limb assist and rehabilitation training includes an upper limb frame, a shoulder joint mechanism, and an elbow joint mechanism which are driven by utilizing a processing unit, a first angle sensing unit, a second angle sensing unit, a first proportional pressure valve, a pressure sensing unit and a pneumatic muscle device. The exoskeleton apparatus can be independently used as an upper limb exoskeleton assistive device or can be combined to form an upper limb exoskeleton rehabilitation training system to simulate the upper limb movements in daily life through the upper limb frame to assist with the movements of the wearer's upper limbs, accomplishing the rehabilitation training of each upper and lower arm joint and neurological function.