There is provided a vehicle seat core member that is superior in terms of a dimensional accuracy as well as integrity of a thermoplastic resin expanded beads molded body and a frame member. A vehicle seat core member (100) is formed as an integrally molded article of a thermoplastic resin expanded beads molded body (10) and a frame member (20), the thermoplastic resin expanded beads molded body (10) is formed of thermoplastic resin expanded beads (30) having through holes (32), and a porosity of the thermoplastic resin expanded beads molded body (10) is 10 vol % or more and 40 vol % or less.