The brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae) is polyphagous pest insect, originated in East Asia including Korea, China, Japan and Taiwan, injuring leguminous and fruit plants and many ornamental trees. Usually stink bugs need legumes as food to complete their life cycle. In particular, in Jeju, the damage of H. halys is frequently found in the environment-friendly citrus cultivation, thus, this study was conducted to find out whether the full life history of H. halys can be completed in an organic citrus orchard with non-heated cultivated greenhouse. In organic ‘Shiranui’ (brand name Hallabong ((Citrus unshiu x C. sinensis) x C. reticulata)) orchard grown in non-heated greenhouse, seasonal fluctuation of each developmental stages of H. halys and its preferring host sites were investigated by visual counting method. The adult population peaks (summer generation) occurred in mid-July for the first generation and late-October for the second generation. Most H. halys was found on young leaves of shoots before fruit coloring (September) with few-individuals were observed on fruits, while thereafter the fourth to fifth nymphs of H. halys moved to citrus fruits for feeding resulting in the fruit drop. Consequently, it was found that H. halys can complete its life cycle in the citrus without special legumes.