A heat exchanger includes a heat exchange tube (10) and a first water collecting tank (20). The first water collecting tank (20) is provided on the heat exchange tube (10), a first water diversion hole (21) is provided at a bottom portion of the first water collecting tank (20), the heat exchange tube (10) passes through the first water diversion hole (21), and the first water diversion hole (21) has a diameter greater than an outer diameter of the heat exchange tube (10). By providing the first water collecting tank (20), and making the heat exchange tube (10) pass through the first water diversion hole (21) provided on the first water collecting tank (20), and leaving a gap between the heat exchange tube (10) and the first water diversion hole (21), the water in the first water collecting tank (20) evenly flows into the first water diversion hole (21).