Seed shattering is an undesirable characteristic of rice cultivars affecting field loss of grain yield before and during harvesting. This research was designed to clarify the inheritance of the cracking characteristics of abscission layers formed between the rice grains and its pedicel using $F_2$ populations derived from the crossing of Milyang 23 and Ashahi. The results indicated that the cracking characteristic of Milyang 23 was dominant to absence of cracking in Ashahi, and controlled by a single dominant gene. The degrees of grain shedding were somewhat related with the cracking characteristics of the abscission layer. The breaking tensile strengths closely correlated with the diameter of the supporting zone, the thickness of sclerenchyma tissue between the inner side of abscission layer and the central vascular tissues in the lemma side, and in the palea side, respectively. Some negative correlations were observed between the breaking tensile strengths and some agronomic traits such as plant height, culm length, panicle length, number of matured grains, and the ratio of fertility.