Provided are: an epoxy resin composition that gives a carbon fiber-reinforced composite material having excellent moldability, heat resistance, and mechanical properties such as tensile strength and compressive strength; and a prepreg. An epoxy resin composition containing at least the following constituent elements [A]-[D]. The epoxy resin composition contains 5-50 parts by mass of constituent element [A] and 20-95 parts by mass of constituent element [B], as well as 1-25 parts by mass of constituent element [C], relative to 100 parts by mass of the total amount of epoxy resin. Constituent element [A] is an epoxy resin having primarily two epoxy groups and one or more condensed polycyclic aromatic hydrocarbon skeletons within a repeating unit of a specific structure; [B] is a glycidylamine epoxy resin having three or more glycidyl groups in the molecule; [C] is a sulfone or imide thermoplastic resin; and [D] is an epoxy resin curing agent.