Japanese hornfaced bee, Osmia cornifrons (Radoszkowski) (Hymenoptera: Megachilidae) is an important pollinator of apple in spring. Since it overwinters as diapause adult, temporal synchronization of bee emergence and apple blooming is critical. We experimented the temperature and relative humidity effect on the emergence of O. cornifrons adults using cold-stored population. Experimental conditions were 10, 15, 20, 25, 30, and 35°C, and 33, 43, and 52% RH. relatively. The adult emergence was early in higher temperature. Relative humidity did not influence the emergence period and the survival as well. The male emerged earlier than the female. The mortality was higher in 10°C (60%) and 35°C (40%) while it remain relatively constant (5∼10%) in other temperatures. Based on this results, further development of adult emergence phenology model will help better timing of the Japanese hornfaced bee use in apple pollination.