A buried type semiconductor laser 1 is made of a p-type InP substrate 2 and includes a ridge section 6 made up of a p type InP first clad layer 3, AlGaInAs distorted quantum well active layer 4 and n type InP second clad layer 5 laminated one atop another. On both sides of the ridge section 6, an buried current block layer 10 made up of a p-type InP first buried layer 7, n-type InP second buried layer 8 and semi-insulating Fe-doped InP third buried layer 9 laminated one atop another is formed. A top face of the third buried layer 9 is covered with an n-type InP semiconductor layer 11. The above structure can suppress the occurrence of a leakage current path on the top face of the third buried layer 9 and improve reliability of the buried type semiconductor laser.