A vehicle lower portion structure comprising: a pair of rocker panels (14, 16) extending along a vehicle front-rear direction, the rocker panels being respectively arranged on both outer sides of a vehicular floor panel in a vehicle width direction; and an electric power supply device (20, 82) arranged below the floor panel, wherein: the rocker panel includes an outer portion, an inner portion, and a first shock absorbing portion; the outer portion is positioned to define an outer wall of the rocker panel in the vehicle width direction; the inner portion is formed integrally with the outer portion, is positioned inward of the outer portion in the vehicle width direction, and forms a closed sectional portion with the outer portion; and the first shock absorbing portion extends in the vehicle width direction from the outer portion to the inner portion in the closed sectional portion and is disposed to overlap the electric power supply device in vehicle side view, characterized in that: the electric power supply device is a storage battery; the storage battery is provided with a battery case accommodating a plurality of battery modules; and a first cross member extending along the vehicle width direction is disposed to overlap the first shock absorbing portion in vehicle side view in the battery case, and in that: the first shock absorbing portion includes a first lateral wall (40A, 40B) extending in the vehicle width direction; and the first cross member includes a second lateral wall (76B, 76D) overlapping the first lateral wall (40A, 40B) extending in the vehicle width direction in vehicle side view. a pair of rocker panels (14, 16) extending along a vehicle front-rear direction, the rocker panels being respectively arranged on both outer sides of a vehicular floor panel in a vehicle width direction; and an electric power supply device (20, 82) arranged below the floor panel, wherein: the rocker panel includes an outer portion, an inner portion, and a first shock absorbing portion; the outer portion is positioned to define an outer wall of the rocker panel in the vehicle width direction; the inner portion is formed integrally with the outer portion, is positioned inward of the outer portion in the vehicle width direction, and forms a closed sectional portion with the outer portion; and the first shock absorbing portion extends in the vehicle width direction from the outer portion to the inner portion in the closed sectional portion and is disposed to overlap the electric power supply device in vehicle side view, the rocker panel includes an outer portion, an inner portion, and a first shock absorbing portion; the outer portion is positioned to define an outer wall of the rocker panel in the vehicle width direction; the inner portion is formed integrally with the outer portion, is positioned inward of the outer portion in the vehicle width direction, and forms a closed sectional portion with the outer portion; and the first shock absorbing portion extends in the vehicle width direction from the outer portion to the inner portion in the closed sectional portion and is disposed to overlap the electric power supply device in vehicle side view, the electric power supply device is a storage battery; the storage battery is provided with a battery case accommodating a plurality of battery modules; and a first cross member extending along the vehicle width direction is disposed to overlap the first shock absorbing portion in vehicle side view in the battery case, the first shock absorbing portion includes a first lateral wall (40A, 40B) extending in the vehicle width direction; and the first cross member includes a second lateral wall (76B, 76D) overlapping the first lateral wall (40A, 40B) extending in the vehicle width direction in vehicle side view.