To provide a production process of resin foam, which allows easy production of a resin foam with an excellent surface appearance and a high foaming rate.

The production process of resin foam is a production process of a resin foam which comprises: a fusion process (I) to heat fuse a thermoplastic resin composition, a gas supply process a(II) to supply an inert gas quantatively to the fused resin composition, a kneading process (III) to blend/knead the inert gas with the fused resin composition, a cooling process (IV) to cool thus kneaded object and a foaming process (V) to foam the kneaded object; wherein the foaming process (V) comprises a cell generating process (V-a) to generate cells and a foam producing process (V-b) to perform growth of the generated cell and surface leveling. A die (especially a circular die) is preferably used when foaming the cooled kneaded object in the foaming process (V).