A lateral light emitting device is developed. The lateral light emitting device is free from variations and degradation in beam quality and reduction in reliability caused by adhesive, can be easily produced, and has a small outer diameter in order to be usable for a thin blood vessel and the like. The above described problem is solved by the lateral light emitting device, which includes an optical fiber, a rod lens fused to an end of the optical fiber, and a prism having a polygonal section fused to a distal end surface of the rod lens.
