PROBLEM TO BE SOLVED: To obtain the subject filler capable of being simply produced at an ordinary concrete plant and capable of maintaining a stable quality by compounding cement with sand and concentrated sludge water in a prescribed compounding ratio. SOLUTION: This filler comprises (A) a cement calculated in a prescribed weight ratio, (B) sand calculated in a prescribed weight ratio, and (C) concentrated sludge water calculated in a prescribed weight ratio and obtained by concentrating sludge water generated on the washing of a concrete-treating facility into a prescribed concentration. The filler is preferably obtained through a sludge water separation process for separating sludge water from the washing drainage of the concrete-treating facility, a sludge water concentration process for concentrating the sludge water separated from the sludge separation process into a prescribed concentration, and a kneading process for kneading the component A, the component B and the component C in prescribed amounts, respectively.
