We have investigated the effects of light quality and CO₂ concentration (0.04% and 10%) on growth of Euglena as a fundamental study. Useful nutrients such as high quality protein and fatty acid, as well as specific saccharide (β-1,3 glucan), contained in Euglena are now being highlighted. In the present study, we investigated the effects of light quality and CO₂ concentration on the production of protein, paramylon and fatty acid. Under the CO₂ concentration of 0.04%, protein contents in Euglena cultured in red and blue light were 105.0 μg 10⁶ cells^-1, paramylon 48.2 μg 10⁶ cells^-1, and in blue light fatty acid was 20.3 μg 10⁶ cells^-1, higher than those in other light conditions. Whereas under the CO₂ concentration of 10%, protein contents in Euglena cultured in red and blue light were 125.6 μg 10⁶ cells^-1, paramylon 57.6 μg 10⁶ cells^-1, and in blue light fatty acid 29.7 μg 10⁶ cells^-1, higher than those in ordinary air conditions (with 0.04% CO₂). No significant differences in these nutrient contents were found between the four light quality treatments under the CO₂ concentration of 10%. As previous data we showed growth of Euglena depended on chlorophyll contents, protein and paramylon contents depended on chlorophyll contents, too. It was concluded that Euglena would be good nutrition source when they are cultured in each light conditions under CO₂ concentration of 10%, so CO₂ discharged from industrials, power stations and so on, will be utilized to this new food production system, effectively.