Organic insulator, metal-clad laminate and wiring board

An organic insulator, comprising an organic resin phase as a main component,

• the organic resin phase comprising a weather-resistant stabilizer,
• the organic resin phase comprising an inner region and a surface region formed in at least one surface of the inner region,
• the surface region having a higher content ratio of the weather-resistance stabilizer than the inner region,
• wherein the organic resin phase comprises a thermosetting resin,
• and
• wherein the thermosetting resin is a cured material of a resin composition comprising a cyclic olefin copolymer having a crosslinkable functional group in a molecule,
• a monomer having at least two ethylenic unsaturated groups in a molecule,
• and a peroxide having a benzene ring in a molecule.