Abstract: An optically adjusting device adapted to be used in a projector is provided. The optically adjusting device includes a frame having a plurality of frame members to define a space for containing an optical combiner therein, a plurality of light-receiving plates, each of which is disposed on one of the frame members for receiving a specific light beam and outputting the specific light beam to the optical combiner, and a plurality of adjusting plates, each of which is arranged between one of the frame members and a corresponding light-receiving plate for sequentially adjusting a position and orientation of the corresponding light-receiving plate with respect to the optical combiner.