A vehicle-body structure of a vehicle comprising a pair of left and right side sills including a side sill outer and a side sill inner, the side sill outer and the side sill inner being joined along a vehicle width direction and forming a closed cross-section extending in a vehicle front-rear direction, wherein the side sill inner comprises: an inner body formed so as to have an open cross-section open on a vehicle-width-direction outer side, the open cross-section extending in the vehicle front-rear direction; and an inner front end connected to a front end of the inner body and facing to each of a pair of left and right front wheels so as to serve as a front end portion of the side sill, the side sill outer comprises: an outer body formed so as to have an open cross-section open on a vehicle-width-direction inner side, the open cross-section extending in the vehicle front-rear direction; and an outer front end connected to a front end of the outer body and facing to each of the pair of left and right front wheels so as to serve as a front end portion of the side sill, characterized by that the inner body of the side sill inner, the outer body of the side sill outer, the inner front end of the side sill inner, and the outer front end of the side sill outer are configured in such a manner that deformation strength against a pressure load from a vehicle front side decreases stepwise in this order. a pair of left and right side sills including a side sill outer and a side sill inner, the side sill outer and the side sill inner being joined along a vehicle width direction and forming a closed cross-section extending in a vehicle front-rear direction, wherein the side sill inner comprises: an inner body formed so as to have an open cross-section open on a vehicle-width-direction outer side, the open cross-section extending in the vehicle front-rear direction; and an inner front end connected to a front end of the inner body and facing to each of a pair of left and right front wheels so as to serve as a front end portion of the side sill, the side sill outer comprises: an outer body formed so as to have an open cross-section open on a vehicle-width-direction inner side, the open cross-section extending in the vehicle front-rear direction; and an outer front end connected to a front end of the outer body and facing to each of the pair of left and right front wheels so as to serve as a front end portion of the side sill, characterized by that the inner body of the side sill inner, the outer body of the side sill outer, the inner front end of the side sill inner, and the outer front end of the side sill outer are configured in such a manner that deformation strength against a pressure load from a vehicle front side decreases stepwise in this order. an inner body formed so as to have an open cross-section open on a vehicle-width-direction outer side, the open cross-section extending in the vehicle front-rear direction; and an inner front end connected to a front end of the inner body and facing to each of a pair of left and right front wheels so as to serve as a front end portion of the side sill, the side sill outer comprises: an outer body formed so as to have an open cross-section open on a vehicle-width-direction inner side, the open cross-section extending in the vehicle front-rear direction; and an outer front end connected to a front end of the outer body and facing to each of the pair of left and right front wheels so as to serve as a front end portion of the side sill, characterized by that the inner body of the side sill inner, the outer body of the side sill outer, the inner front end of the side sill inner, and the outer front end of the side sill outer are configured in such a manner that deformation strength against a pressure load from a vehicle front side decreases stepwise in this order. an outer body formed so as to have an open cross-section open on a vehicle-width-direction inner side, the open cross-section extending in the vehicle front-rear direction; and an outer front end connected to a front end of the outer body and facing to each of the pair of left and right front wheels so as to serve as a front end portion of the side sill, characterized by that the inner body of the side sill inner, the outer body of the side sill outer, the inner front end of the side sill inner, and the outer front end of the side sill outer are configured in such a manner that deformation strength against a pressure load from a vehicle front side decreases stepwise in this order.