Disclosed is an invention relating to a beam for a bumper. The disclosed invention comprises: a rail member, installed on a chassis, which is formed by processing a continuous fiber-reinforced composite material into a rail shape, has coupling parts having flange-shaped engagement surfaces formed on both sides thereof in the longitudinal direction; stay members which are provided at both sides ofthe rail member in the longitudinal direction and respectively coupled to the coupling parts so as to be positioned between the chassis and the rail member, and are formed by processing a continuous fiber-reinforced composite material into a stay shape, wherein flange-shaped coupling surfaces parallel to the coupling surfaces of the coupling parts are coupled to the coupling surfaces of the coupling parts, thereby being coupled with the rail member; and fastening plates which are provided between the coupling parts and the stay members to reinforce the rigidity of the coupling surfaces betweenthe stay members and the chassis.