A tunnel reinforcing member is attached to a front floor tunnel. Second upper wall and second side walls of the tunnel reinforcing member are connected to a first upper wall and first side walls of the front floor tunnel, respectively, such that spaces are formed between second edge portions of the tunnel reinforcing member and first edge portions of the front floor tunnel. A rear portion of the first upper wall of the front floor tunnel faces a lower wall of a cross member with a kick-up part in between. A rear portion of the second upper wall of the tunnel reinforcing member inclines upwards and rearwards so as to be separated apart from the first upper wall of the front floor tunnel and faces a section reinforcing member fixed to the cross member with the kick-up part in between.