Disclosed is a polybenzoxazime precursor and a method of preparing the same. The polybenzoxazime precursor is used to prepare a hardened material having improved thermal characteristics, having high thermal and flame-retardant characteristics while maintaining its excellent electrical characteristics, or having high thermal and electrical characteristics, thus being available for use in a copper clad laminate, a semiconductor encapsulate, a printed circuit board, an adhesive, a paint, and a mold.