An electronic device has a heat source and a thermal module. The thermal module includes a plurality of radiating fins respectively provided with a through hole, and a heat pipe structure having a pipe body. The pipe body has a vaporizing section in contact with the heat source and a condensing section extended through the radiating fins via the through holes thereon. The vaporizing section has a first pipe thickness and is internally provided with a first wick structure to define a first flow channel. The condensing section has a second pipe thickness smaller than the first pipe thickness, and is internally provided along part of its length with at least one second wick structure to define at least one second flow channel communicating with the first flow channel.