PURPOSE: To obtain a small-sized and high-stability device, by providing an acoustooptic optical modulating element where plural ultrasonic exciting parts are arranged in parallel on an acoustooptic medium, a means which makes the optical beam flat or divides it to plural optical beams, optical beam transmitting means, etc.

CONSTITUTION: The optical beam from a light source 26 such as a laser is converted to a flat optical beam or is divided to plural optical beams by an optical beam flat forming equipment 29 consisting of a pair of cylindrical lenses 27 and 28. These optical beams are modulated by an acoustooptic optical modulating element 30 where plural ultrasonic exciting parts are arranged in parallel on one acoustooptic medium, and plural optical beams emitted from the element 30 are transmitted to a focusing lens system 34 through plural optical beam transmitting means 32. Otherwise, optical beams from said optical modulating element 30 are led to optical beam transmitting means 32 through a reduction optical system consisting of minute lenses 31.