A heat exchanger comprising: a plurality of tubes; core plates (24, 25) to which the plurality of tubes are bonded; and tank members (27, 28) connected to the core plates, wherein an edge of the core plate and an edge of the tank member are connected to each other by a clamping section, the clamping section has a plurality of claws (35, 235) provided on the edge of the core plate, an edge portion (41, 441) provided on an opening end of the tank member, and a waved wall provided in the tank member along a length direction in a wave shape, the waved wall has a waved outer surface that is provided on an outer surface above the edge portion and that includes a plurality of outer ridge portions and a plurality of outer valley portions which are disposed alternately, and a waved inner surface that is provided on an inner surface of the tank member and that includes a plurality of inner ridge portions and a plurality of inner valley portions which are disposed alternately, the plurality of outer valley portions are capable of receiving the claw and have a step difference portion in contact with the claw, which is formed on the edge portion, the inner ridge portion is positioned inside the outer valley portion in a width direction, and an inner width (Wir) of the tank member regulated by the inner ridge portion is narrower than a width of the tube, characterized in that the inner ridge portion is not positioned between the adjacent tubes and is positioned between the tubes in the extension of the tubes in the height direction, and the inner valley portion provides a space in the extension of the tube in the height direction. a plurality of tubes; core plates (24, 25) to which the plurality of tubes are bonded; and tank members (27, 28) connected to the core plates, wherein an edge of the core plate and an edge of the tank member are connected to each other by a clamping section, the clamping section has a plurality of claws (35, 235) provided on the edge of the core plate, an edge portion (41, 441) provided on an opening end of the tank member, and a waved wall provided in the tank member along a length direction in a wave shape, the waved wall has a waved outer surface that is provided on an outer surface above the edge portion and that includes a plurality of outer ridge portions and a plurality of outer valley portions which are disposed alternately, and a waved inner surface that is provided on an inner surface of the tank member and that includes a plurality of inner ridge portions and a plurality of inner valley portions which are disposed alternately, the plurality of outer valley portions are capable of receiving the claw and have a step difference portion in contact with the claw, which is formed on the edge portion, the inner ridge portion is positioned inside the outer valley portion in a width direction, and an inner width (Wir) of the tank member regulated by the inner ridge portion is narrower than a width of the tube, characterized in that the inner ridge portion is not positioned between the adjacent tubes and is positioned between the tubes in the extension of the tubes in the height direction, and the inner valley portion provides a space in the extension of the tube in the height direction.