A bunk bed equipped with a guard rail, has a bed board frame, two side bed frames respectively disposed at the front and rear sides of the bed board frame to support the bed board frame and a guard rail disposed at the side of the bed board frame. The guard rail includes a first rail frame, a second rail frame and a rotating mechanism. The rotating mechanism connects the first rail frame and the second rail frame, such that the two rail frames rotate relatively in the horizontal direction or the longitudinal direction. The first rail frame is locked to the second rail frame by a lock mechanism to form a guard rail entirety. The rotating mechanism moveably connects the first rail frame and the second rail frame, the first rail frame and the second rail frame are locked by a lock mechanism to form a detachable guard rail.