An inflatable device (7, 8, 9) which can fit with a portable SPA pool and has the advantages of low costs, a light weight and convenience for carrying and storage, and can serve as a step for a user to conveniently enter and exit the inflatable pool, a desk on the side of the SPA pool for placing personal articles and a stool for a user to rest near the portable SPA pool. An inflatable device (7, 8, 9) for a portable SPA pool, comprising: a top sheet (1) and a bottom sheet (3) spaced apart from each other in a vertical direction; side walls (2) extending between said top sheet (1) and said bottom sheet (3), upper edges (201) of said side walls (2) being connected to outer edges (100) of said top sheet (1), respectively, and lower edges (200) of said side walls (2) being connected to outer edges (300) of said bottom sheet (3), respectively so as to form an inflatable air chamber (4); and at least one group of tensioning structures (5), said tensioning structures (5) being disposed in said air chamber (4) and connected to said top sheet (1), said bottom sheet (3) and said side walls (2) respectively so as to limit the outward bulging of said top sheet (1), said bottom sheet (3) and said side walls (2) when said air chamber (4) is inflated.