PROBLEM TO BE SOLVED: To provide an insolubilization material for insolubilizing nitrogen and phosphorus contained in soil such as bottom mud recovered from lake capable of insolubilizing both of nitrogen and phosphorus at large percentage.SOLUTION: There is provided an insolubilization material for nitrogen and phosphorus containing magnesium oxide having Blaine specific surface area of 5,000 cm/g or more and zeolite having Blaine specific surface area of 2,000 cm/g or more with mass ratio of zeolite/magnesium oxide of 0.1 to 100.SELECTED DRAWING: None