A falling film evaporator (100), a housing (101) thereof being accommodated with a heat exchange tube (304), a perforated plate (205) and a spraying tube (202), the perforated plate (205) being provided between the spraying tube (202) and the heat exchange tube (304), such that refrigerant sprayed from the spraying tube (202) is sprayed onto the surface of the heat exchange tube (304) by means of distribution of the perforated plate (205); spraying openings (301) on the spraying tube (202) have a strip shape, and the extension direction of the openings is perpendicular to the length direction of the spraying tube (202). By means of configuring the length direction of the spraying tube (202) to be substantially perpendicular to the length direction of the heat exchange tube (304), refrigerant sprayed from the spraying openings (301) flows substantially in the length direction of the housing (101), the flow path of the refrigerant being lengthened, avoiding uneven spraying on the surface of the heat exchange tube (304).