Despite potential of hydride-forming alloys for hydrogen storage, there have been few alloys which can reversibly store hydrogen without heating or activation treatment. In this study, a high-entropy alloy is designed for room temperature hydrogen storage based on three criteria: total valence electron concentration (VEC) of 6.4, single-phase thermodynamic stability (examined by CALPHAD calculations) and AB₂H₃ hydride formation (A: hydride-forming elements, B: elements without affinity to hydrogen, H: hydrogen). The designated alloy, TiZrCrMnFeNi containing 95 wt% C14 Laves phase, absorbs and desorbs 1.7 wt% of hydrogen (hydrogen-to-metal ratio: 1) at room temperature with a fast kinetics and without activation treatment.