PURPOSE: To obtain a resin composition useful for a solder resist, excellent in developability, adhesiveness, heat resistance, chemical resistance and electrical insulating property, by mixing a specified alicyclic epoxy resin with an unsaturated compound.

CONSTITUTION: A polycyclohexene oxide polymer having vinyl group side chains, obtained by the ring-opening polymerization of 4-vinylcyclo-hexene-1-oxide in the presence of an initiator such as an alcohol, a phenol, a carboxylic acid or thiol is epoxidized in the presence of an oxidizing agent such as a peroxide to obtain an aliphatic epoxy resin (A) of the formula (wherein R is a residue of an organic compound having at least one active hydrogen in the molecule, and n is 1W30 on the average). 5W80wt.% component A is mixed with 95W20wt.% unsaturated compound (B) (e.g., epoxyacrylate) to obtain a resin composition. To 100pts.wt. this resin composition, 0.1W10pts.wt. photoinitiator, 0.01W5pts.wt. radiation-sensitive catalyst precursor, 0.5W40pts.wt. epoxy curing agent, etc. are optionally added.