A high-electron mobility transistor (HEMT) includes a substrate, a group III-V channel layer, a group III-V barrier layer, a group III-V cap layer, a source electrode, a first drain electrode, a second drain electrode, and a connecting portion. The group III-V channel layer, the group III-V barrier layer, and the group III-V cap layer are sequentially disposed on the substrate. The source electrode is disposed at one side of the group III-V cap layer, and the first and second drain electrodes are disposed at another side of the group III-V cap layer. The bottom surface of the first drain electrode is separated from the bottom surface of the second drain electrode, and the composition of the first drain electrode is different from the composition of the second drain electrode. The connecting portion is electrically coupled to the first drain electrode and the second drain electrode.