The heat transfer device at least comprises: an evaporator, a heat conductor and a connecting pipe. The evaporator comprises: a first hollow tube; a porous core mortised inside the first hollow tube; and a second hollow tube mortised on the first hollow tube. The heat conductor 220 covers the evaporator. The heat conductor is on the heating device. The connecting pipe is connected to first and second hollow tubes. The connecting pipe is used for containing a working fluid. The condenser is on the connecting pipe. The porous core, the first and second hollow tube, and the heat conductor are mortised together so as to simplify the manufacturing process, and reduce the cost. Further, the evaporator is tightly covered and fixed by the heat conductor so that the heat generated by the heating device can be uniformly conducted to the evaporator to enhance the heat conductivity.