In order to investigate an effect of excreta energy on energy utilization of diet, metabolizable(MEn) and true metabolizable(TMEn) energy of corn starch and soybean meal were studied. Hatched single comb White Leghorn male chicks were fed for the first 11 days on a commercial chick mash and for the subsequent 10 days on diet containing 22.0% of cotton meal(cellulose diet) and diets subsetituted 17.0% of cellulose with corn starch(starch diet) and soybean meal (protein diet) in cellulose diet, respectively. When birds were fed protein diet, body weight gain was higher and feed: gain ratio was lower than those fed cellulose and starch diets. Ratio of MEn to gross energy, MEn/GE, was 72, 83 and 77% for cellulose, starch and protein diets, respectively. While rate of productive energy(PE) to MEn, PE/MEn, was 27.0% for cellulose diet which was decreased to 21.0% in starch diet, and 35.0% for protein diet. Corn starch showed 83.0% of MEn/GE which was higher than 39.0% for soybean meal. PE was minus value in corn starch but which was 2149 cal for soybean meal having 132.4% of PE/ MEn. TMEn/MEn was 101.2 - 101.4% for cellulose and starch diets, which was increased to 101.8% for protein diet, Soybean meal had 107.0% of TMEn/MEn which was higher than 100.2% for corn starch. Birds fed protein diet excreted higher urinary energy(UE), metabolic fecal energy (FEm) and endogenous urinary energy(UEe) than those fed starch and cellulose diets, which was resulted in the low MEn for soybean meal.