Korea has been developing hydrogen energy technology to enhance its energy security. The Hydrogen Energy R&D Center established by the Korean government invested about 100 billion Korean won (KRW) into the development of hydrogen energy technology from 2003 to 2012. This study uses input-output (I-O) analysis, along with the scenario-based exogenous specification method, to investigate the effect of hydrogen energy technology investment on the Korean economy for the period 2020-2040. We focus on two perspectives: (1) the sectoral linkage effect and (2) the sectoral impacts of hydrogen energy supply investments. The overall results reveal that the hydrogen sector can be characterized as intermediate primary production because of its high backward and forward linkage effects. By 2040, total production in the hydrogen sector under two scenarios will be 13,484 and 2979 billion KRW, respectively. This study is a pioneering study into the assessment of the economy-wide effects of Korea's hydrogen energy industries.