A method for manufacturing a compound semiconductor epitaxial substrate with few concave defects is provided. The method for manufacturing a compound semiconductor epitaxial substrate comprises a step of epitaxially growing an InGaAs layer on an InP single crystal substrate or on an epitaxial layer lattice-matched to the InP single crystal substrate under conditions of ratio of V/: 10-100, growth temperature: 630.degree. C.-700.degree. C., and growth rate: 0.6 .mu.m/h-2 .mu.m/h.