An hydrogen tank filling apparatus includes a first hydrogen supply pipe for supplying hydrogen substantially at an atmospheric temperature from a high-pressure hydrogen storage tank to a hydrogen tank, a second hydrogen supply pipe for supplying cooled hydrogen from the high-pressure hydrogen storage tank to the hydrogen tank, and an internal tank temperature measuring unit for measuring the temperature inside the hydrogen tank. The first hydrogen supply pipe and the second hydrogen supply pipe are selectively switched by a control unit, depending on changes in the temperature inside the hydrogen tank.