A foam molding apparatus and a foam molding method thereby are proposed. The foam molding apparatus includes a foaming agent supply unit configured to supply a foaming agent, a molten resin supply unit configured to supply molten resin, a fixed mixing unit configured to produce a foaming resin-critical solution by mixing a foaming agent supplied from the foaming agent supply unit and molten resin supplied from the molten resin supply unit through a rod-shaped body, and a molding unit configured to mold a foam molding product using the foaming resin-critical solution supplied from the fixed mixing unit. Accordingly, it is possible to produce a foaming resin-critical solution by uniformly mixing a large amount of high-viscosity gel-state molten resin and a high-pressure compressed and low-viscosity foaming agent, using high-strength multiple channels.