PURPOSE: A fishway for a weir in a river is provided to achieve buoyancy and durability by embedding a hollow sphere and a support and to reduce water resistance by controlling the entrance according to changes in water level. CONSTITUTION: In a fishway body(15), a passage pipe(31) is assembled at an entrance/exit(11) and fixed with a frame(29) between a bearing(37) and a housing(27). A safety net fixed with a frame(29') is installed at the entrance/exit. The fishway body comprises inner and outer walls, and a support wall and a reinforcing element which are formed between the inner and outer walls to provide buoyancy. The entrance/exit are formed to face each other about a weir(35'). An expansion unit of inverted horn shape is attached to the entrance/exit to reduce the flow rate in the fishway.
