To provide a scum removing device which is improved such that the structure of the device is simplified, the flow of scum is smoothed and the facility can be easily installed.

The scum removing device includes: a weir 13 which is disposed so as to be moved vertically across the water level 7 as a boudary in a sedimentation basin 1; a trough 10 being a scum attracting/leading out part which can make the attracted scum S effluent; and a driving means 37 which vertically drives the weir 13, wherein the driving means 37 which is installed on the basin as an electromotive means and is driven by solar electric generation.