PROBLEM TO BE SOLVED: To provide a rotating device for muddy water, capable of improving the sealing function and durability of a seal part thereof.SOLUTION: The rotating device for muddy water includes: a container 2; a rotation shaft 4 which penetrates the container 2; the seal part 5 disposed between the container 2 of the stationary side and the rotation shaft 4 of the rotation side; and a foreign matter entry prevention part 7 (a pump 25, a high-pressure water supply line 26 and an outflow port 27) which prevents fine slag as foreign matter in slag hopper water 8 (muddy water) from entering the seal part 5. As a result, the rotating device for muddy water can prevent the fine slag from entering the seal part 5 by means of high-pressure water flowing out from the outflow port 27. Thereby, the rotating device for muddy water can improve the sealing function and durability of the seal part 5.