An HM reservoir for storing hydrogen includes a housing and a plurality of storage units. The storage units are stacked in the interior of the housing. Each storage unit includes a pair of plate-like molded bodies and a flat heat exchanger. The plate-like molded bodies are formed by compressing powder of hydrogen storage material. The heat exchanger is provided between the molded bodies. Each molded body includes a first side and a second side, which is opposite to the first side. The first side contacts the heat exchanger. A plurality of flat hydrogen passages are formed in the interior of the housing to face the second sides of the associated molded bodies. The structure of the HM reservoir is thus simple. Further, the molded bodies of the HM reservoir smoothly absorb hydrogen and smoothly release the same.