A glass-containing molding composition is prepared by incorporating glass powder into a thermoplastic resin at a glass load ratio of 40 to 70 percent by weight, in which the glass powder is composed of solid spherical glass particles which have an average particle size of 10 to 40 μm and whose surfaces are totally covered with a silane compound and which exhibits reduction ratios of melt flow rate on a parabolic curve with the increase of glass load ratios and has a reduction ratio of melt flow rate of 3/4 to 1/4 within a glass load ratio in a range of 40 to 64 percent by weight.