The Waste Rice Straws (W.R.S.) after cultivation with the Pleurotas Ostreatus SACCARDO was substituted for wheat bran in the broiler ration. The results of the experiment 1 and 2 obtained were summerized as follows; 1. The content of C. protein in the W.R.S. showed 1.5% higher value than that in the rice straw. No change was detected in the content of C. fat. However the content of C. fiber and N.F.E in W.R.S. decreased in comparision with those of raw rice straw. 2. The treated groups were inclned to rapid gain of body weight, especially the 4% W.R.S. group had been showed significatly higher value of gain than the control and 6% treated groups (p＜0.05 ). 3. No significant differences were observed in the amount of feet intake among experimental groups, even if the treated groups showed slightly higher intake than control group. 4. The treated groups in W.R.S. were inferior to the control group in feed intake but there were no significant differences. 5. The methionine in W.R.S. was the only amino acid which contained similar quantity of wheat brans. 6. To extend the amount of W.R.S. in broiler ration the 6% of W.R.S. was substituted for wheat bran and methionine mixture was added. No significance differences had been showed in weight gain, feed intake and feed efficiency between control and treated groups. Even though the treated groups showed more feed intake and lower weight gain in comparision with control group. 7. The methionine added group showed adverse effect in economics of production (p＜0.01) because of high cost of the methionine mixture, Therefore less than. 6% of the WRS could be substituted for wheat bran. According to the results of the experiment 1 and 2 it could be concluded that maximum use of the W.R.R. as substitute for wheat bran was less than 4% of the ration.