A laser diode capable of reducing a radiating angle θ⊥ in the vertical direction, an optical pickup device, an optical disk apparatus, and optical communications equipment, all equipped with the laser diode which increases optical coupling efficiency. It has a first cladding layer of the first conductive type formed on a substrate, with an active layer on top of the first cladding layer and a second cladding layer of the second conductive type on top of the active layer. In at least the first or second cladding layer, it is formed of at least one optical guide layer having a higher refractive index than the first or second cladding layer and operating to expand a beam waist in the waveguide. This operation contributes to widening a region in which to shut up light, enabling a radiating angle θ⊥ in the vertical direction to be reduced.