To provide a styrene resin compsn. not deteriorating transparency and surface appearance, and excellent in mechanical characteristics and heat deflection temp. under load.

This is a styrene resin compsn. contg. a styrene resin and a silane clay complex, and the silane clay complex is prepared by introducing a silane compd. represented by the formula: YnSiX4-n [wherein n is an integer of 0-3, Y is a 1-25C hydrocarbon group or an org. functional group comprising a 1-25C hydrocarbon group and a substitute group, and X is a hydrolysable group and/or a hydroxide group and n pieces of Y and (4-n) pieces of X may be the same or different kind] to a swelling silicate, and an average thickness of the silane clay complex layer in the styrene resin compsn. is not greater than 500 .