This study was carried out to evaluate the productivity of rice cultivation in extremely late season in Korea and to confirm the effects of pot-raising seedling culture in this case by assessing the growth and yield performance of rice cultivars that are well adapted to late culture. Suitable cultivars for extremely late culture should not have premature heading habit when transplanted around late July and also secure appropriate growth duration before heading. Geumobyeo 1 and Manjongbyeo showed small decrease in the emerged leaves in transplanting in late July or early August and heading occurred at the same time relatively without premature heading. At transplanting from late July to early August in extremely late rice cultivation, ripening was relatively good until transplanting on August 5. At transplanting on July 30, accumulated temperature from heading to the first frost was $853^{circ}C$ and ripening was good enough. However, heading was delayed by low temperature at transplanting on August 10 and ripening was very poor due to low accumulated temperature of below $800^{circ}C$, causing drastic decrease of rice yield. The rice yield increased in transplanting with pot seedling, especially the effects of pot seedling was higher in Geumobyeo 1, but panicle number was not enough to secure rice yield owing to short growth duration. In order to cultivate rice in extremely late season, we should select adaptive rice cultivars that have suitable growth duration and excellent ripening in low temperature. Here, pot-seedling did a great role to secure early growth and bigger growth amounts.