This paper presents the power-density development of a high-frequency isolated DC-DC converter for ICT equipments. This technique results in a prototype of a 5MHz DC-DC converter module. In order to realize a prototype of the high-frequency isolated DC-DC converter, its topology is selected to be a half-bridge type current-mode resonant converter, and switching power devices of GaN-FET and Si-SBD and the transformer composed of a nickel-zinc ferrite core are utilized. As a result, a 5MHz isolated DC-DC converter with the input/output voltages of 48V/12V and the power rating of 120W has been fabricated, and the high power-density of 14W/cm3 has been performed.