In a heat exchanger including a plurality of tubes 1 through which a first fluid passes, a housing 2 in which the tubes 1 are installed, and sealing members for sealing a second fluid that flows over surfaces of the tubes 1, the housing 2 includes an inlet 4 for introducing the second fluid therein and a first outlet 5 and second outlets 6 for discharging the second fluid, and the sealing members include a first sealing member 3a positioned on one of end sides of the tubes 1, a second sealing member 3b positioned on the other end side of the tubes 1, and a third sealing member 3c positioned between the first and second sealing members 3a and 3b. The third sealing member 3c is provided so that a gap 7 is provided between the first sealing member 3a and the third sealing member 3c while another gap 7 is provided between the second sealing member 3b and the third sealing member 3c, and that a flow path for the second fluid is formed therein. The second outlets 6 are provided so as to be connected to the gaps 7.