<p>Disclosed is a semiconductor laser provided with: a lower cladding layer (14) which has a first conductivity type and is an AlGaAs layer; an active layer (18) which is provided on the lower cladding layer (14) and comprises a plurality of quantum dots; and an upper cladding layer (22) which has a second conductivity type the opposite of the first conductivity type and which comprises a first AlGaAs layer (74), second AlGaAs layer (76), and third AlGaAs layer (78) stacked in that order on the active layer (18). The second AlGaAs layer (76) and third AlGaAs layer (78) form an independent ridge section (26), and the first AlGaAs layer (74) remains at the two sides of the ridge section (26). The Al composition ratio at the second AlGaAs layer (76) is larger than the Al composition ratio at the first AlGaAs layer (74) and at the third AlGaAs layer (78).</p>
