A transition joint which blocks insulating oil by connecting a three core HPFF cable and a three core XLPE cable is provided. The transition joint includes three epoxy units which connect independently three first cable cores constituting the three core HPFF cable and three second cable cores constituting the three core XLPE cable, respectively. Each of the epoxy units includes a center electrode connecting an electrode of the first cable core and an electrode of the second cable core, and an epoxy molding part implemented in the form of surrounding an outer wall of the center electrode in order to block the center electrode from the insulating oil.