For evaluation of biological effect of $p^+(50.5MeV)$ Be neutron beam produced by Korea Cancer Center Hospital (KCCH) cyclotron the RBE had been measured in experimental tumor Walker 256 carcinosarcoma as well as normal tissue, mouse intestine and bone marrow, in single and fractionated irradiation. As pilot study, the RBE had been measured for the mouse jejunal crypt cells in single whole body irradiation of which the result was 2.8. The obtained RBE values of TCD 50 of Walker 256 tumor, bone marrow and intestine En single irraiation were 1.9, 1.9 and 1.5 respectively. In fractionated irradiation, the RBE value of tumor Walker 256 was decreased as increasing of fraction number and increased as increaing of fraction size.