To provide a method for catalytically cracking waste plastics wherein the efficiency in decomposition is high; even polyethylene composed of linear chain molecules difficult in decomposition is decomposable at a low temperature and decomposed residue is hardly produced; the process is simple since dechlorination can be achieved at the same time with catalytically cracking waste plastics in one reaction vessel; and oil fractions can be recovered at 50% or more on a net yield basis. The method for catalytically cracking waste plastics of the present invention has a constitution in which waste plastics are loaded as a raw material into a granular FCC catalyst heated to a temperature range from 350° C. to 500° C. inside a reaction vessel, thereby decomposing and gasifying the waste plastics in contact with the FCC catalyst.