The present invention provides a heat exchanger, comprising a plurality of first heat exchange plates (1) and second heat exchange plates (2) that are connected sequentially and at an interval; the first heat exchange plates (1) and the second heat exchange plates (2) each comprise a heat exchange sheet (3) and a heat exchange frame (4) disposed on side ends of the heat exchange sheet (3); the side ends of the heat exchange sheet (3) are formed with a snap projection (9) in a direction away from the heat exchange frame (4); the heat exchange frame (4) is formed with a snap groove (10); the first heat exchange plates (1) and the second heat exchange plates (2) are in interference connection through the engagement between the snap projection (9) and the snap groove (10); an air channel (5, 6) is formed between a first heat exchange plate (1) and an adjacent second heat exchange plate (2), the air inlet of the first heat exchange plate (1) and the air inlet of the second heat exchange plate (2) have different directions, and the air outlet of the first heat exchange plate (1) and the air outlet of the second heat exchange plate (2) have different directions. The present invention puts the first heat exchange plate (1) and the second heat exchange plate (2) in interference connection through the engagement between the snap projection (9) and the snap groove (10), which effectively ensures stability and reliability of the connection, and ensures the airtightness of the connection.