We synthesized novel monofunctional and bifunctional benzoxazines having imide groups. Brown-colored transparent films were obtained by curing the benzoxazines up to 240 ºC. Monofunctional benzoxazine gave brittle film, but bifunctional benzoxazine gave tough film. Viscoelastic analysis revealed that glass transition temperature of the polybenzoxazine film obtained from the bifunctional benzoxazine was 289 ºC, about 90 ºC higher than that of a typical polybenzoxazine. Thermogravimetric analyses revealed that the introduction of imide groups was also effective to improve the thermal stability of polybenzoxazines.