Disclosed is a method which is not hazardous unlike an aqueous sodium hypochlorite solution and can effectively deactivate or inactivate a calicivirus (e.g., a norovirus) contained in a material to be sterilized even in the co-presence of an organic material mainly composed of a protein. Specifically disclosed is a method for inactivating a calicivirus in the co-presence of a protein, which comprises contacting a material which is suspected of containing a calicivirus and contains a protein with a composition which comprises an aqueous solution containing ethanol and an acid as active ingredients and having pH 2.5 to 5.0. The calicivirus is, for example, a norovirus.
