Effects of deformation rate on the mechanical properties of epoxy resin used in superconducting magnets have been studied at cryogenic temperatures. Compressive and flexural tests were made to reveal the mechanical behaviors. In the case of compressive tests, the increase of deformation rate caused the increase of elastic modulus and the decrease of breaking stress and strain. In the case of flexural tests, different results in breaking stress was obtained. The results indicate that following two problems must be elucidated for practical use of polymers, i.e. (i) impact strength of the polymers, (ii) the stress condition applied to the polymers in the magnet.