A heat pipe includes a tubular member, a capillary wick, and a liquid. The tubular member has a plurality of capillary ditches formed on an internal sidewall thereof. The capillary wick is disposed on the internal sidewall of the tubular member and located on openings of the capillary ditches for covering and sealing the ditches. The liquid is contained inside the tubular member. The capillary wick and ditches provide the liquid with larger cross-sectional area for the capillary action to enhance guidance of the liquid and to further enhance the thermally conductive efficiency.