A window drain for preventing stains on a building wall and damage caused by frozen rain water, which is installable and sealable easily without impairing the appearance of a building. The present invention relates to a window drain adapted to be positioned at the portion beneath each vertical post of a sash window frame comprising a vertical portion, a sloping portion, a front portion and a horizontal portion for latching itself to an upper portion of an external wall. Further, the present invention relates to the window drain, wherein the horizontal portion has a notch at an end thereof and a sealing pocket. Further, the present invention relates to a window drain, further comprising upstanding portions to regulate a stream of water so that the water is kept between the upstanding portions, at both ends of the window drain wherein one upstanding portion is located at the inner side of the vertical portion of a sash window frame, and the other upstanding portion is located at the outer side of the vertical portion of a sash window frame.