To provide a filter sand washing device for manganese sand, which utilizes the mass produced products abundantly, is inexpensive and excellent in reliability and durability, and further can change a washing capacity flexibly.

One or more stirrers 15... having a rotary vane 17 are detachably and exchangeably provided in series on a passing sand path 11 sending the filter sand made to be manganese sand together with water, and further a rotating speed of each stirrer is controllable. Manganese is separated by the facing-up of the sand each other, or of the sand and vanes. Since the stirrer is a mass production good, the whole device becomes inexpensive, and the reliability and durability are also high. Further, the washing capability is controlled by changing the rotating speed of the stirrer, and the number of the installed devices.