A water trampoline includes an air cushion having predetermined size and buoyancy; a supporting ring detachably connected to a top surface of the air cushion, and including a lower ring having a diameter corresponding to that of the top surface of the air cushion, and an upper ring located above the lower ring by a predetermined height; and a jumping bed tightly stretched over the upper ring by a plurality of radially extended elastic elements. The jumping bed is located above the air cushion instead of in a central open space thereof, and therefore has effectively increased surface area and largely enhanced bearing strength to enable safer and more durable use of the water trampoline.