Bisphenol A-based benzoxazine that contained oligomers (oligo-Ba) was prepared from bisphenol A, formaline, and aniline. Curing reaction of oligo-Ba with bisoxazoline and the properties of the cured resin were investigated. Consequently, the ring-opening reaction of benzoxazine ring occurred, and then the phenolic hydoroxyl group generated by the ring-opening reaction of benzoxazine ring reacted with oxazoline ring. It was found that the cure induction time and cure time of the molten mixture from oligo-Ba and bisoxazoline could be reduced and also the cure temperature could be lowered, compared with those from bisphenol A-based benzoxazine, which contained no oligomers (Ba), and bisoxazoline. The melt viscosity of the molten mixture from oligo-Ba and bisoxazoline was kept 0.1-10 [Pas] at 140 degreesC even after 40 min, the molten mixture from oligo-Ba and bisoxazoline showed good flowability below 140 degreesC as well as that from Ba and bisoxazoline. However, above 160 degreesC the curing reaction of oligo-Ba with bisoxazoline proceeded more rapidly than that of Ba with bisoxazoline. The cured resin from oligo-Ba and bisoxazoline showed good heat resistance and water resistance, compared with the cured resin from Ba and bisoxazoline.