Optical waveguides, lens arrays and laser collecting devices are disclosed. The optical waveguide is formed with an output surface which is made smaller in dimension in a fast axis direction than an input surface. The waveguide collects in the fast axis direction plural laser beams output from plural laser emitting parts arranged in the fast axis direction and outputs from the output surface. The entrance surface of the optical waveguide is provided with first lenses to correspond respectively to the plural laser emitting parts. Each of the first lenses is located to be offset first predetermined distances from a corresponding one of the laser emitting parts in the beam traveling direction and in said fast axis direction, and the first predetermined distances are determined for each of the first lens in taking into account the focal length of each first lens and an angle which each first lens makes with the output surface of the waveguide.