To provide a purifying agent for polluted water, polluted soil, or a waste material, capable of purifying the environment, without containing a hazardous material as a component, nor being affected by a pollutant, capable of sustaining a purifying effect, having high safety, and capable of being given at a low cost, and to provide a method for purifying the same.

This purifying agent for the polluted water, the polluted soil, or the waste material contains (b) 20-45 pts.wt. of sodium thiosulfate and (c) 50-75 pts.wt. of water based on (a) 5 pts.wt., when converted into silver, of silver oxide [provided that a total amount of the components (a), (b), and (c) is 100 pts.wt.].