In this paper, a three-dimensional numerical study on flow pattern in winter along connecting passageway of a composite building was conducted using a commercial CFD package. The incompressible Navier-Stokes equation coupled was solved by using SIMPLE algorithm in order to find steady solutions. It was shown that a upward flow is generated inside the building in winter due to buoyancy effect and that the air inside connecting passageway flows from the shorter building to the taller one regardless of the slope of the passageway. Further, it was found that the magnitude of air velocity inside connecting passageway increases as the uphill slope to the taller building increases and decreases as the downhill slope to the taller one increases, although the variation in the magnitude of fluid velocity is not substantial. Lastly, it was shown that the maximum air velocity inside connecting passageway is less than the allowable limit for all the cases considered in this study.