A semiconductor laser has a semiconductor substrate, a lower cladding layer formed on the semiconductor substrate, an active layer disposed above the lower cladding layer, a first upper cladding layer disposed above the active layer, a second upper cladding layer disposed above the first upper cladding layer and having a mesa structure, a high-order mode filter layer formed on both side faces of the second upper cladding layer, continuously extending from the both side faces onto at least a part of a side region on both sides of the second upper cladding layer and having a band gap not exceeding a band gap of the active layer, and a block layer formed on the high-order mode filter layer and on a side region on both sides of the second upper cladding layer and including a layer having a band gap greater than a band gap of the active layer.