A method of manufacturing a semiconductor laser according to an aspect of the present invention includes (a) sequentially epitaxially growing a first cladding layer, an active layer and a second cladding layer on a semiconductor substrate composed of InP or GaAs and having a plane index of (100), (b) forming a plurality of growth start surfaces having a plane index greater than (100) in an upper surface of the second cladding layer, and (c) epitaxially growing a third cladding layer containing zinc in the plurality of growth start surfaces of the second cladding layer.