The invention discloses a side dumping hopper of a loader, and relates to the technical field of engineering machinery. The side dumping hopper of the loader comprises a hopper wall plate, hinging seats, hinging seat plates and box-shaped rib plates, wherein the hinging seat plates are installed at a symmetrical position of a central surface of the hopper wall plate; the adjacent hinging seat plates splay along the hopper wall plate in an included angle of 40-60 degrees; the hinging seats are installed on the inner sides of the two hinging seat plates respectively; one end of each hinging seat is connected with the hopper wall plate; the other end of each hinging seat is connected with the corresponding hinging seat plate; the upper surface and the lower surface of each box-shaped rib plate are closed by cover plates to form a box shape; hinging holes are formed on the upper cover plate and the lower cover plate. Compared with the prior art, the hinging seat plates are connected with the central surface of the hopper wall plate to form 40-60-degree included angles, so that because of proper pre-deformation, the stress is enhanced and a welding seam is unlikely to crack; the hinging seats are arranged on the hinging seat plates, and the box-shaped rib plates play a strengthening role.