A rubber modified styrene-based resin is provided that is excellent in oil resistance, folding endurance, and tear strength and that is preferably used for a food container and a food container lid member not cracking by repeated fitting. According to the present invention, a rubber modified styrene-based resin is provided that contains rubbery dispersed particles, having a volume median particle diameter from 4.0 to 10 μm and a gel component from 22.0 to 35.0 mass %; a matrix phase having a weight average molecular weight (Mw) from 150 thousand to 300 thousand; and a methanol soluble component from 1.5% to 4.0%.