In order to investigate the biological value (BV) of the protein of earthworm cake which is a dried residue after the fractionation of supernatants from Lumbricidae Eisenia Foetida (earthworm) heated at 180 - 190℃, the hatched White Leghorn male chicken were fed with a commercial diet for the first 8 days, protein-free basal diet For the next 6 days and experimental diets for the subsequent 6 days. The experimental diets contained the earthworm cake of 2.5, 5.0, 7.5, 10.0 and 15.0%r and 7.5 and 10.0%, of fishmeal or milk casein, respectively. Urinary nitrogen was calculated from the nitrogen content of uric acid, total creatine and ammonia in excretes of chick. Nitrogen intake and nitrogen balance per day were increased according as the graded level of the earthworm cake protein was increased. Daily urinary nitrogen(y) per bird correlated exponentially with the daily nitrogen intake(X) as a regression equation of y=11.7e^(0.005344X)(r=0.952**). Also daily fecal excreted nitrogen(y) correlated with nitrogen intake(X) as a regression equation of y=3.38e^(0.01227X)(r=0.863*). It means that the endogenous urinary nitrogen (EUN) is 11.7㎎ and metabolic fecal nitrogen(MFN) is 3.38㎎ per day if the chicks will be fed protein-free diet. The BV calculated using the EUN and MFN were 86.5% in average and apparent digestibility of the protein were 85.8% in average. Those values were not affected by the graded levels of protein content in diets. But true digestibility of the protein was over 100% when the diets contained 2.0% of the protein, which was gradually decreased according to the contents of the protein increased, showing 87.1% when the diets contained 10.4% of protein. Then the value of net protein utilization was reached to 86.1% when the diets contained 2.0% of the protein, which was decreased to 74.8% when the diet contained 10.4% of the protein. And the nitrogen balance(y) also correlated linearly with the absorbed nitrogen as a regression equation of y=0.869x-9.83 (r=0.999**). Then nitrogen balance index was 0.869 of which hundred magnificence, 86.9, was similar with the BV. When the chicks were fed diets contained 5.1 and 6.5% of fishmeal protein, respectively, the true digestibility were 92.8 and 96.5% and the BV were found as 91.3 and 81.8, respectively. And the chicks fed diets contained 7.4 and 9.0% of milk caseine have shown 89.6 and 87.8% of the true digestibility and 90.2 and 89.4% of the BV, respectively. Thus, in this experiment, the digestibility and biological value were not shown any significant difference among the earthworm cake, fishmeal and milk casein protein.