It is pointed out that out-of-plane buckling of buckling-restrained braces whose connections have low stiffness or strength may occur. However, the design criteria to prevent out-of-plane buckling proposed in past is based on the experiment with small out-of-plane story drift. In this paper, cyclic loading test of buckling-restrained brace under largely bidirectional story drift is conducted. Through the test, effects of stiffness and strength of the connections, and loading direction on the ultimate failure of the braces are clarified. Further, design criterion to prevent yielding splice plates is proposed and validated based on the test results.