A vehicle body structure which includes a side sill extending on a side of a vehicle body in a front-rear direction, and a pillar having a lower end joined to the side sill and extending upward; wherein the side sill comprises: a side-sill outer which is formed, to have a hat-like cross section, by a pair of an outer upper wall and an outer lower wall which face each other, an outer side wall which extends to outer ends, in a vehicle-width direction, of the outer upper wall and the outer lower wall, an outer upper flange which extends upward from an inner end, in the vehicle-width direction, of the outer upper wall, and an outer lower flange which extends downward from an inner end, in the vehicle-width direction, of the outer lower wall; and a side-sill inner which is formed, to have a hat-like cross section, by a pair of an inner upper wall and an inner lower wall which face each other, an inner side wall which extends to inner ends, in the vehicle-width direction, of the inner upper wall and the inner lower wall, an inner upper flange which extends upward from an outer end, in the vehicle-width direction, of the inner upper wall, and an inner lower flange which extends downward from an outer end, in the vehicle-width direction, of the inner lower wall; wherein the outer upper flange and the inner upper flange are joined and the outer lower flange and the inner lower flange are joined so as to form a closed cross section; characterized in that the pillar comprises: a joined portion located in a lower end portion of the pillar, and sandwiched and joined between the outer upper flange and the inner upper flange; a first extended portion and a second extended portion which extend in the closed cross section of the side sill from the joined portion, and are arranged at a predetermined distance from each other in the front-rear direction; and an extension (41, 42) which has an upper end joined to at least one of the first extended portion and the second extended portion, and a lower end sandwiched and joined between the outer lower flange and the inner lower flange. a side-sill outer which is formed, to have a hat-like cross section, by a pair of an outer upper wall and an outer lower wall which face each other, an outer side wall which extends to outer ends, in a vehicle-width direction, of the outer upper wall and the outer lower wall, an outer upper flange which extends upward from an inner end, in the vehicle-width direction, of the outer upper wall, and an outer lower flange which extends downward from an inner end, in the vehicle-width direction, of the outer lower wall; and a side-sill inner which is formed, to have a hat-like cross section, by a pair of an inner upper wall and an inner lower wall which face each other, an inner side wall which extends to inner ends, in the vehicle-width direction, of the inner upper wall and the inner lower wall, an inner upper flange which extends upward from an outer end, in the vehicle-width direction, of the inner upper wall, and an inner lower flange which extends downward from an outer end, in the vehicle-width direction, of the inner lower wall; wherein the outer upper flange and the inner upper flange are joined and the outer lower flange and the inner lower flange are joined so as to form a closed cross section; characterized in that the pillar comprises: a joined portion located in a lower end portion of the pillar, and sandwiched and joined between the outer upper flange and the inner upper flange; a first extended portion and a second extended portion which extend in the closed cross section of the side sill from the joined portion, and are arranged at a predetermined distance from each other in the front-rear direction; and an extension (41, 42) which has an upper end joined to at least one of the first extended portion and the second extended portion, and a lower end sandwiched and joined between the outer lower flange and the inner lower flange.