PURPOSE: To provide a forming device for a filmlike beam having high efficiency for utilizing a light beam from a light source and exactly irradiating an object with a bright beam keeping a set length.

CONSTITUTION: This device comprizes a light source 11, a convex cylindrical lens 15 having a focus line at right angle to the projecting direction of a light beam 14 emitted from the light source 11 and converting the beam 14 to the parallel beam 14 with the focus line along the projecting direction and a concave cylindrical lens 16 having a focus line at right angle to that of the convex cylindrical lens 15 and spreading the beam 14 transmitted through the convex cylindrical lens 15 in the film shape along the focus line of the convex cylindrical lens 15 and a collimating optical system 17 converting the beam 14 dispersed in the film shape after passing through the concave cylindrical lens 16 into the film-shaped beam 14 parallel with the projecting direction.