PROBLEM TO BE SOLVED: To provide styrene-modified thermoplastic polyester resin particles which can yield a foam molding having realized goals of (1) ameliorating the poor chemical resistance attributed to the existence of a styrenic resin, (2) ameliorating the poor rigidity attributed to the existence of an olefinic resin, (3) further improving the heat resistance and rigidity of the styrene-modified polyolefinic resin, and (4) ameliorating the poor moldability attributed to the existence of a polyester-based resin (polycarbonate-based resin) while improving the expansion ratio.SOLUTION: The styrene-modified thermoplastic polyester resin particles of the present invention include 100 pts.wt. of particles of a thermoplastic polyester-based resin having a glass transition point of 90 to 135°C and at least 100 pts.wt. and no more than 1000 pts.wt. of a polystyrene-based resin, whereas the polystyrene-based resin is dispersed, in a particulate state, within the particles of the thermoplastic polyester-based res
