Abstract: A heat exchanger includes: first plates; second plates disposed at intervals with each between a pair of the first plates adjacent to each to alternately form first flow paths and second flow paths; and a heat exchange promoting member in the first flow paths. At least one of the first plates and each second plate includes a plurality of protruding portions each of which is formed in a V shape in a plan view such that the protruding portion recesses in a corresponding one of the first flow paths and projects in a corresponding one of the second flow paths. Each protruding portion has a tip end portion and an opening portion arranged in a flow direction in the second flow path, and one of a pair of free end portions is positioned on a first inflow port side and the other is positioned on a first outflow port side.