A first semiconductor laser emitting light with a first wavelength and a second semiconductor laser emitting light with a second wavelength are formed on an identical substrate. Each of the semiconductor lasers includes: a doublehetero structure in which at least a first-conductivity-type cladding layer, an active layer and a second-conductivity-type cladding layer are stacked in this order; and a ridge waveguide including at least an upper portion of the second-conductivity-type cladding layer and a contact layer formed on the second-conductivity-type cladding layer. A first-conductivity-type current blocking layer is formed on both side walls of each of the ridge waveguides and on a portion around each of the ridge waveguides, and a leakage preventing layer is formed on the current blocking layer.