[en] In this study, we investigated the biological damage and stress responses induced by ion beam (proton beam) irradiation as a basis for the development of protective measures against space radiation. We examined the biological effects of proton beam produced by MC-50 cyclotron at KIRAMS on the cultured cells and animals(mice). The proton beam energy used in this study was 34.9Mev and the absorption dose rate for cells and mice were 5.509Gy/sec and 0.65Gy/sec, respectively. The cell survival rates measured by plating efficiency showed the different sensitivity and dose-relationship between CHO cells and Balb/3T3 cells. HGPRT gene mutation frequency in Balb/3T3 was 15x10^-6/Gy, which was similar to the reported value of X-ray. The expression and activation patterns of stress signaling proteins in Balb/3T3 cells showed that IκB-α decreased markedly, whereas p53, phospho-p53, Rb increased after proton beam irradiation, which implied that the stress signaling pathways were activated by proton beam irradiation. In the experiments with animal (C57BL/6 mouse), the immune cells (white blood cell, lymphocyte) were greatly reduced, while the red blood cell and platelet did not change in the peripheral blood of mice following proton beam irradiation. Also, the total antioxidant status was greatly decreased at 4 hours after irradiation, which suggested that proton beam irradiation induces strong oxidative stress in the body. These research results can be utilized as a basic biological data for the study on the biological space radiation effects and the application of ion beams to life sciences using MC-50 cyclotron