Though many papers have reported the nutrition value of Chlorella their results are all different because of the differences in processing method. To investigate its processing and nutrition value we provided the white rats with the Chlorella that were treated with boiling methanol. The results obtained in this investigation are summarized as follows: Two groups. which were fed with 20% Chlorella protein and 10% Chlorella plus 0.37% $_{DL}-methionine$ gained less weight than the 10% egg protein group but equaled the 20% egg protein group in weight gain. The digestion rates calculated from ordinary N-balance method were 83.6% for 20% Chlorella, 81.7% for 10% Chlorella, and 84.9% for 10% Chlorella plus methionine group. This value is lower than 20% Egg (93.8%) and 10% Egg group (89.6%) Biological values from this method were 78.3% for 20% Chlorella and 79.1% for 10% Chlorella group, being lower than 20% Egg (85.2%), 10% Egg (93.2%). But the biological value of 10% Chlorella group was markedly enhanced to 92.2%, a value comparable to that of 10% Egg group, by adding methionine.