A heat storage device (1) of the present disclosure includes: a heat storage container (10) having an inlet (2) and an outlet (3) for a heat medium; a plate-like heat storage body (4) disposed in the heat storage container (10) and having a heat storage material (4a) and an envelope (4b) containing the heat storage material (4a); a plate-like spacer (6) placed on the heat storage body (4) in the heat storage container (10) and having a plurality of contact portions (6a) that are in contact with the heat storage body (4) and a plurality of non-contact portions (6b) that are spaced from the heat storage body (4), the contact portions (6a) and the non-contact portions (6b) being alternately formed in a specific direction; and a plurality of flow paths (5) for leading the heat medium from the inlet (2) to the outlet (3), the flow paths being formed by a surface of the heat storage body (4) and the non-contact portions (6b) and extending in a direction intersecting the specific direction. Thereby, the heat transfer characteristics between the heat storage material and the heat medium are good.