PURPOSE: To obtain a compatibilizer which can give a thermoplastic resin composition well balanced among the properties and capable of giving a molding good in appearance and transparency by melt reacting a hydroxy compound highly compatible with polypropylene with an acid-containing methacrylic resin.

CONSTITUTION: The compatibilizer is obtained by melt reacting a composition comprising 5-95wt.% hydroxy compound highly compatible with polypropylene and 95-5wt.% methacrylic resin containing at least one acid and/or acid anhydride. The objective composition well balanced among the properties and excellent in appearance and transparency is obtained by mixing 100 pts.wt. resin component comprising 5-95wt.% polypropylene and 95-5wt.% methacrylic resin obtained by polymerizing methyl methacrylate or a mixture thereof with 0.1-20 pts.wt. this compatibilizer.