A laser beam oscillating apparatus which includes a plurality of semiconductor laser beam oscillators (21, 22, 23) oscillating laser beams of a different wavelength from each other, an optical waveguide (12) formed on a substrate (11) so that the oscillated laser beams propagate therein and are then emitted in the same direction from the output end thereof and an optical coupler (13) to introduce the laser beams into the optical waveguide, thus allowing simultaneous introduction of these semiconductor laser beams of different wavelengths into the optical waveguide and simultaneous output of them in the same direction from the output end thereof.