This application provides a resin composition and an adhesive. The resin composition is composed of benzoxazine and a resin. The benzoxazine is synthesized from a primary amine-capped flexible polyimide oligomer, an aldehyde and a monofunctional phenolic compound. The resin contains one or more of an epoxy resin, a maleimide resin, and a cyanate ester resin containing two or more functional groups. The resin is 0.1%-70% by weight of the benzoxazine.