PURPOSE: A ventilator for a sliding window is provided to maximize convenience and safety by the selective operation of the ventilation and the opening of a window and to maximize the esthetic performance since a ventilating unit is not externally exposed if the window is closed. CONSTITUTION: A ventilator for a sliding window comprises a fixed frame(10), a movable frame(20), a first locking unit and a second locking unit. The fixed frame is installed on the inserting groove(3) in a window frame(2). The movable frame is overlapped with the fixed frame and externally slides by a given distance to make the hanging movement. The movable frame comprises a plurality of vents in a longitudinal direction. The first locking unit pulls the rotating knob of a window(5) and automatically unlocks the window and the window frame. The second unit automatically unlocks the window and the movable frame by the operation of the opening/closing knob of the window.
