To provide a primer composition excellent in weatherability and adhesion properties and used especially for adhesion between an automotive one-pack moisture-cured urethane sealant and an adherend.

A primer composition contains a film-forming reactive resin comprising a vinyl polymer as a main chain and isocyanate groups and alkoxysilyl groups as side chains, carbon black and an organic solvent. The primer composition preferably contains 5-40 wt.% of the reactive resin, 2-20 wt.% of carbon black and 40-93 wt.% of the organic solvent.