This application provides an evaporative cooling unit. The evaporative cooling unit includes an outdoor channel, an indoor channel, and a heat exchange apparatus, and, further includes: an air filter and a defrosting apparatus that are disposed in the outdoor channel. The defrosting apparatus is located on a side that is of the air filter and that is close to an air intake vent of the outdoor channel. The defrosting apparatus includes a heat exchange film, and the heat exchange film has a first channel and a second channel that are arranged crosswise. The first channel communicates with the air intake vent of the outdoor channel, the second channel communicates with the indoor channel, and the first channel communicates with the second channel. The defrosting apparatus further includes a switch valve, and the switch valve is configured to control the second channel to communicate with the indoor channel.