A vehicle seat core material includes a molded article that includes thermoplastic resin expanded beads. The molded article has a substantially rectangular shape in a top view, and has a front side and a rear side opposite the front side. The molded article has an average density (Z) of 20 kg/m3 to 50 kg/m3. The molded article includes, on the rear side of the molded article, a rear thin portion having a thickness of 10 mm to 40 mm, the thickness of the rear thin portion being smaller than an average thickness of the molded article. A ratio (Y/Z) of a density (Y) of the rear thin portion to the average density (Z) of the molded article is 1.05 to 3. The rear thin portion of the molded article has a fusion rate of 70% or more.