PURPOSE: To provide a method for producing lutein by Chlorophyta, capable of increasing lutein content in a cell by efficiently producing lutein by Chlorophyta.

CONSTITUTION: (1) A CO2-containing gas is fed to a medium containing NO3- as a nitrogen source and PO43- as phosphoric acid and Chlorophyta is cultured so as to have ≥0.5g/l cell concentration and each ion concentration of NO3- and PO43- in the medium is lowered to ≤1/2 to culture the Chlorophyta. (2) A gas containing 1-40% CO2 is fed to a medium containing nutritive salts and Chlorophyta are cultured so as to have ≥0.5g/l cell concentration and a metal ion is added to the medium and air is fed thereto instead of CO2-containing gas and culture is carried out. (3) A CO2-containing gas is fed to the medium containing nutritive salts and Chlorophyta are cultured so as to have ≥0.5g/l cell concentration and at least one kind of NO2 gas, SO2 gas and ozone is mixed into CO2 gas.