The invention relates to a ventilation device (1), comprising a ventilation housing that is provided with one or more profiles (4) that are contiguous to an indoor environment (2) and one or more profiles (5) that are contiguous to an outdoor environment (3), comprising an air through-flow channel (6), and comprising a rebate (7) of a window, the ventilation housing being provided for installation in said rebate (7), the rebate (7) comprising a stop and/or a glazing bead (8), the window being provided so as to screen off the abovementioned indoor environment (2) from the abovementioned outdoor environment (3), and the abovementioned one or more profiles (4) of the ventilation housing that are contiguous to the indoor environment (2) running on in their longitudinal direction until behind the corresponding glazing bead or stop (8) of the rebate (7). With such a ventilation device (1), water penetration from the outdoor environment (3) to the indoor environment (2) is prevented at various degrees of inclination of the ventilation device (1).