To provide a sedimented sludge amount measuring instrument capable of measuring accurately a sedimentation amount of sludge such as polluted sediment, irrespective of skill of a measuring person, even when the sedimentation amount of the sludge such as the polluted sediment is difficult to be estimated because of that in a natural environment such as a river, an estuary, a lake front and the like.

This sedimented sludge amount measuring instrument for measuring the sedimentation amount of the sedimented sludge includes a reference rod 1 for determining a reference for measuring the sedimentation amount; a sludge level contact body 2 fixed with one end of the reference rod 1 in its central part, and for level-contacting with a surface of the sludge; and a measuring rod 3 slidable in parallel to the reference rod 1. The sludge level contact body 2 is a hollow body in which an outer circumferential length in a cross section orthogonal to a longitudinal direction of the reference rod 1 is gradually increased along with a distance from the fixed portion of the reference rod 1, and has one or plurality of hole parts 4 for inserting the measuring rod 3.