A pneumatic elastic band includes an outer portion, an inflatable portion and a nozzle. The outer portion has a strip-shaped structure with elasticity. The inflatable portion includes a plurality of expansion portions and a plurality of communication portions. Each of the communication portions is connected between two of the expansion portions adjacent to each other for defining a plurality of gaps. The nozzle is disposed on a surface of the outer portion and communicated with the inflatable portion. When a gas is guided into the inflatable portion through the nozzle, the plurality of expansion portions of the inflatable portion are inflated to fill the gaps and make the inflatable portion contract inwardly, so that the outer portion contracts inwardly and deforms, wherein when the gas is guided out of the inflatable portion, the inflatable portion is deflated and loosened to return to an uninflated state to loosen the shoe.