A heat exchanger 100, including: an inner cylinder 10 through which a first fluid can flow, the inner cylinder 10 being configured to house a heat recovery member 30; and an outer cylinder 20 disposed so as to be spaced on a radially outer side of the inner cylinder 10 such that a second fluid can flow between the outer cylinder 20 and the inner cylinder 10. In the heat exchanger 100, at least a part of the outer cylinder 20 and/or the inner cylinder 10 has at least one continuous irregular structure 40.