To provide a method for producing a resin molded article which hardly involves the occurrence of optical distortion and of sink marks.

The method for producing the resin molded article includes: a first step of pouring a polyfunctional (meth)acrylic monomer into a molding mold and irradiating the polyfunctional (meth)acrylic monomer with radiant energy rays until a polymerization conversion ratio reaches 1-10% to polymerize a part of the polyfunctional (meth)acrylic monomer; and a second step of heating the polymerized polyfunctional (meth)acrylic monomer after the first step in such a state that the polymerized polyfunctional (meth)acrylic monomer is held in the molding mold to further polymerize a remaining part of the polyfunctional (meth)acrylic monomer until the polymerization conversion ratio reaches 60% or more.