An optical scanning apparatus includes a first optical member for receiving a plurality of light beams with an interval and for causing a first group of beams to emerge with a narrower interval, the first optical member being rotatable to adjust the interval of the beams emergent therefrom; a second optical member for receiving a second light beam and the first group of beams emergent from the first optical member with an interval and for causing a third group of beams to emerge with a narrower interval, the second optical member being rotatable to change the interval between the first group of beams and the second beam; and deflecting means for scanningly deflecting a third group of beams emergent from the second optical member.