To provide an efficient fluid power transmission device by utilizing fluid characteristics to the maximum extent.

This continuous and limitless variable transmission has a casing provided with an inlet hole 12 (or an outlet hole 16), the casing contains an input shaft 17 and an output shaft 18 connected by a series of coaxial cages 22, the cages are alternately connected to the input shaft 17 and the output shaft 18, and the other shafts are maintained so as to rotate freely. The cage is provided or includes a series of blades, and this blade performs mutual action with transmission medium travelling in a predetermined direction (single or a plurality) between an inlet and an outlet in the casing so that the blade undergoes changes of an angular momentum of the transmission medium. Curvature of the blade is reversed depending on whether these cages are cages on input side or cages on output side.