PURPOSE: To deflect and scan an optical beam over a wide range through simple constitution by arranging plural optical beam deflecting elements along the incidence ath of the optical beam and providing a driving means which deflects the beam selectively in a specific direction different from the incidence direction.

CONSTITUTION: Numbers of split electrodes 2 are provided in an isolated state successively at the inside of the upper facing wall 1a of a housing 1 charged with a transparent liquid medium, and a heating body 3 is provided while connected to their tips. When the heating body 3 connected to the split electrodes 2 is conducted electricty by a driving part 4a to generate heat according to a picture signal inputted to a control circuit 4, air bubbles formed on the surface reflect the incident laser beam 8b irregularly. Slits 5 made in the lower facing wall 1a' corresponding to electrodes 2 collect the scattered light 8c. Therefore, the optical beam is scanned over the wide range according to the picture signal; the constitution is simplified, the deflection optical path is short, and the device is miniaturized.