A curable resin composition which is easily cured by heating or ultraviolet irradiation and capable of forming a thick cured film due to low shrinkage. This curable resin composition enables to obtain a cured product satisfying various characteristics such as heat resistance, chemical resistance, high surface hardness and high refractive index. Also disclosed is a cured product obtained from such a composition. Specifically disclosed is a curable resin composition containing at least one substance selected from the group consisting of condensates (A) obtained by hydrolyzing and condensing a thiol group-containing alkoxysilane (a1) represented by the following general formula (1): R1Si(OR2)3 (1) (wherein, R1 represents a hydrocarbon group having at least one thiol group and 1-8 carbon atoms or an aromatic hydrocarbon group having at least one thiol group, and R2 represents a hydrogen atom, a hydrocarbon group having 1-8 carbon atoms or an aromatic hydrocarbon group), compounds (B) having an epoxy group, compounds (C) having an isocyanate group and compounds (D) having a carbon-carbon double bond.