A thermal storage device having a plurality of tube^like first thermal medium branch pipes (5) into which a first thermal medium (3) flows and a thermal storage material (l) provided on the outer peripheries of the first thermal medium branch pipes (5) is characterized by including a first header (6) that communicates with the upper portions of the first thermal medium branch pipes (5) and allows the first thermal medium (3) to flow therethrough, a first upper reservoir (7) that communicates with the first header (6) and stores the first thermal medium (3), and a first inlet (8) that communicates with the first upper reservoir (7) and allows the first thermal medium (3) to flow therethrough. The first upper reservoir (7) is formed in a direction intersecting with the direction of streamline of the first inlet (8).
