A stacking-type header, comprising: a first plate-shaped unit having formed therein a plurality of first inlet flow passages and a plurality of first outlet flow passages; and a second plate-shaped unit being stacked on the first plate-shaped unit and having formed therein: at least a part of a distribution flow passage configured to distribute refrigerant, which passes through a second inlet flow passage to flow into the second plate-shaped unit, to the plurality of first outlet flow passages to cause the refrigerant to flow out from the second plate-shaped unit; and at least a part of a joining flow passage configured to join together flows of the refrigerant, which pass through the plurality of first inlet flow passages to flow into the second plate-shaped unit, to cause the refrigerant to flow out toward a second outlet flow passage, characterised in that the first plate-shaped unit or the second plate-shaped unit comprises at least one plate-shaped member having formed therein: a flow passage through which the refrigerant passes to flow into the plurality of first inlet flow passages; and a flow passage through which the refrigerant passes to flow into the second inlet flow passage, and wherein the at least one plate-shaped member has a through portion or a concave portion formed in at least a part of a region between the flow passage through which the refrigerant passes to flow into the plurality of first inlet flow passages and the flow passage through which the refrigerant passes to flow into the second inlet flow passage. a first plate-shaped unit having formed therein a plurality of first inlet flow passages and a plurality of first outlet flow passages; and a second plate-shaped unit being stacked on the first plate-shaped unit and having formed therein: at least a part of a distribution flow passage configured to distribute refrigerant, which passes through a second inlet flow passage to flow into the second plate-shaped unit, to the plurality of first outlet flow passages to cause the refrigerant to flow out from the second plate-shaped unit; and at least a part of a joining flow passage configured to join together flows of the refrigerant, which pass through the plurality of first inlet flow passages to flow into the second plate-shaped unit, to cause the refrigerant to flow out toward a second outlet flow passage, at least a part of a distribution flow passage configured to distribute refrigerant, which passes through a second inlet flow passage to flow into the second plate-shaped unit, to the plurality of first outlet flow passages to cause the refrigerant to flow out from the second plate-shaped unit; and at least a part of a joining flow passage configured to join together flows of the refrigerant, which pass through the plurality of first inlet flow passages to flow into the second plate-shaped unit, to cause the refrigerant to flow out toward a second outlet flow passage, characterised in that a flow passage through which the refrigerant passes to flow into the plurality of first inlet flow passages; and a flow passage through which the refrigerant passes to flow into the second inlet flow passage, and wherein the at least one plate-shaped member has a through portion or a concave portion formed in at least a part of a region between the flow passage through which the refrigerant passes to flow into the plurality of first inlet flow passages and the flow passage through which the refrigerant passes to flow into the second inlet flow passage.