Disclosed is a lower cross member of a vehicle. The lower cross member includes a core member configured to be disposed on a vehicle floor so as to extend in a width direction of the vehicle, to be formed of a composite material including unidirectional carbon fiber or bidirectional carbon fiber, and to have a cross-section including at least one closed curve, a lower layer configured to extend in an extending direction of the core member, to be disposed between the core member and the vehicle floor, and to be formed of a composite material including a first multi-axial glass fabric, and an upper layer configured to extend in the extending direction of the core member, to be disposed on an upper surface of the core member, and to be formed of a composite material including a second multi-axial glass fabric.