An AB2C2-type ternary hydrogen storage alloy comprising an AB2C2 phase as main ingredient, where A comprises at least one of a rare-earth element and Ca, B mainly comprises Mg, and C comprises at least one of transition metal elements of Cu, Ni, Co, Fe, Cr, Mn, Ti, V and Zn, and x and y represent values within the-ranges of 1.5≦x≦2.5 and 1.5 ≦y≦3.5, respectively; and an AB2C3-type ternary hydrogen storage alloy comprising an AB2C3 phase as a main ingredient, where A comprises at least one of a rare-earth element and Ca, B mainly comprises Mg, and C comprises at least one of transition metal elements of Cu, Ni, Co, Fe, Cr, Mn, Ti, V and Zn, each of which has large hydrogen storage capability and desorbing amount per unit weight and hydrogen storage characteristics excellent in reversibility of the hydrogen absorption and desorption and is provided by improving the stability in a hydride state of an alloy mainly comprising a lightweight metal element and increasing the hydrogen dissociation pressure of the hydride.