A distributed feedback semiconductor laser includes an n-InP substrate, an n-InGaAsP diffraction grating layer above the n-InP substrate, an AlGaInAs-MQW active layer above the diffraction grating layer and a ridge portion on the active layer. The ridge portion includes a p-InP cladding layer and a p-InGaAs contact layer. The wavelength λg corresponding to the bandgap energy of the diffraction grating layer and the oscillation wavelength λ of laser light produced by the laser satisfy the relationship λ−150 nm