A grass collecting apparatus for directing grass clippings cut by a mower unit to a grass catcher. The apparatus includes a grass collecting duct for guiding the grass clippings from the mower unit to the grass catcher, the duct having an outlet portion leading to the grass catcher defined by an upper plate, right and left side plates and a bottom plate, a gate-shaped frame disposed in a boundary between the outlet portion of the grass collecting duct and an opening of the grass catcher, and a swing mechanism for swinging the grass catcher between a grass collecting position and a grass discharging position. The bottom plate is arranged to receive the grass clippings falling off an area when the grass catcher is in the grass collecting position, and is displaced with a surface being tilted when the grass catcher is swung from the grass collecting position to the grass discharging position.