A loop heat pipe includes an evaporator and a closed loop. The evaporator includes an evaporator body made of a heat conductive material. The evaporator body has at least two retaining holes and at least a channel hole penetrating the retaining holes. In addition, the closed loop includes a first pipe body and at least a second pipe body. One end of the first and the second pipe bodies is a heat reception end, which are securely fastened to the two retaining holes of the evaporator. The other end of the first and the second pipe bodies is a heat reception end, thereby sequentially forming a circulating loop. Meanwhile, a flattened liquid seal region is formed between the heat reception end and the connection end of the first pipe body.