To provide a multi-functional and novel rapid dewatering solidification agent to solve a problem in a conventional dewatering method of concentrated sludge.

The rapid dewatering solidification agent for treatment of the concentrated sludge having a high water content comprises blending a main component of 100 pts.wt. including cement of 10 to 50 pts.wt., fly ash of 30 to 80 pts.wt., calcium chloride of 5 to 15 pts.wt., magnesium chloride of 5 to 15 pts.wt. and calcium oxide of 5 to 15 pts.wt. with aluminium sulfate of 5 to 10 pts.wt., calcium sulfate of 15 to 25 pts.wt., magnesium sulfate of 5 to 10 pts.wt., sodium thiosulfate of 5 to 10 pts.wt., an organic flocculant of 0.1 to 0.2 pt.wt. and perlite of 5 to 10 pts.wt. as an assential component.