a second floor cross member that is raised upward from a floor panel forming a floor portion of the vehicle and extends in a vehicle width direction to support a rear portion of a front seat;

a third floor cross member that extends in the vehicle width direction along the second floor cross member at a vehicle body rear of the second floor cross member and is raised upward from the floor panel to support a front portion of a rear seat;

a floor longitudinal frame that extends in a front-rear direction of a vehicle body between the second floor cross member and the third floor cross member;

a battery pack which is arranged under a floor of the floor longitudinal frame and the floor panel, and in which a battery case for accommodating a battery module is vertically fixed to the floor longitudinal frame;

a first floor cross member that extends in the vehicle width direction along the second floor cross member in a vehicle body front of the second floor cross member and supports a front portion of the front seat;

a fourth floor cross member that extends in the vehicle width direction along the third floor cross member at the vehicle body rear of the third floor cross member;

a side sill that is joined to the first floor cross member, the second floor cross member, the third floor cross member, and the fourth floor cross member from an outer side in the vehicle width direction and extends in the front-rear direction of the vehicle body;

a floor tunnel that connects the first floor cross member and the fourth floor cross member in the front-rear direction of the vehicle body and is raised upward from the floor panel to divide the second floor cross member and the third floor cross member into left and right sides in the vehicle width direction; and

a front side frame that extends from the first floor cross member toward a front of the vehicle body;

wherein the front side frame comprises:

a front frame portion that extends in the front-rear direction of the vehicle body:

an outer extension portion that extends outward in an inclined manner in the vehicle width direction from a rear end portion of the front frame portion toward a rear of the vehicle body, and is joined to a front portion of the side sill; and

an inner extension portion that extends inward in an inclined manner in the vehicle width direction from the rear end portion of the front frame portion toward the rear of the vehicle body, and is joined to the first floor cross member,

the front frame portion, the outer extension portion, and the inner extension portion form a Y-shaped frame in a plan view, and

the battery case is arranged inside a rectangular frame body in a plan view formed by the first floor cross member, the fourth floor cross member, and the side sill.