An optical scanning device is adapted to output a light beam, and includes a base, a transmission mechanism, a rotary power source and a holder. The transmission mechanism is disposed on the base. The rotary power source is adapted to generate a rotation and mechanically connected to the transmission mechanism so as to drive the transmission mechanism to generate the rotation. The holder is disposed to the transmission mechanism and includes a first lateral section, wherein when the transmission mechanism and the holder are synchronously rotated, the first lateral section also rotates the output light beam and thus the output light beam forms a light spot having a scanning area projected on a destination.
