Apple bitter rot caused by Glomerella cingulata has been known to occur annually on the fruits of previously infected twigs and the trunks. This study was carried out to ensure whether the pathogen overwinters in the form of perithecium or not. Since the acervuli of the pathogen were formed in inoculated apple trees, it would be possible that the pathogen could overwinter on the twigs, Ascigerous stage was found both under the cuticle of the infected trunk and in outer layers of rotted fruits. Therefore, it could be concluded that the pathogen overwintered in the form of perithecium is a primary inoculum in next year. Ascigerous stage of the appfe bitter rot organism was observed for the first time in Korea.