The invention provides a large-area palladium membrane device for hydrogen isotope separation. According to the device, two palladium-alloy membranes with the same size are overlapped and welded to the left side and the right side, and a two-layer palladium membrane is formed; a center supporting body with the length smaller than that of the palladium-alloy membranes is taken, the upper end of the two-layer palladium membrane is flush with the center supporting body, and the lower end of the two-layer palladium membrane protrudes out of the center supporting body; the center supporting body is wound with multiple circles of cylindrical palladium membrane components in an attached mode, the ends, flush with each other, of the palladium membrane components face upwards, the palladium membrane components are vertically inserted into an assembled flange, the two-layer palladium membrane at the flush ends is welded, and a first welded joint is formed; a gap between the two-layer palladium membrane inserted into the flange and the flange is welded, and a second welded joint is formed; the inner side and the outer side of the two-layer palladium membrane are filled with porous supporting bodies, an annular supporting body is formed, and the large-area palladium membrane device for hydrogen isotope separation is formed. The curved-type palladium membrane components of the device can increase the hydrogen permeation area, increase the purification quantity in unit time and reduce the material cost, and the device is suitable for places of hydrogen isotope separating and recycling in fusion reactors and the like.