<p><P>PROBLEM TO BE SOLVED: To provide a heavy metal-insolubilizing material and a heavy metal-insolubilizing method, which have a high effect of insolubilizing heavy metals even under a high alkali condition, need neither treatment nor pretreatment of a large amount of sludge, and easily carry out the insolubilizing treatment. <P>SOLUTION: The heavy metal-insolubilizing material contains at least one compound selected from the group consisting of hypophosphorous acid, hypophosphite salts, phosphorous acid and phosphite salts. The heavy metal-insolubilizing method is also provided. <P>COPYRIGHT: (C)2013,JPO&INPIT</p>