A vehicle body structure, comprising: a lower panel, including: a lower wall that forms a lower portion of a floor portion, and an outer front wall that is placed to extend upward from a vehicle body front end of the lower wall; and an upper panel, including: an upper wall (40; 44) that forms an upper portion of the floor portion opposite to the lower wall and also forms a closed cross-section shape extending in a front-back direction of the vehicle body, and an inner front wall that is placed to extend upward from the vehicle body front end of the upper wall (40; 44) and joined to the outer front wall and that forms a closed cross-section shape that is connected to the closed cross-section shape extending in the front-back direction of the vehicle body and extends in a vehicle width direction while including both of left and right ends at an upper portion of the outer front wall, the vehicle body structure being characterized in that the lower panel and the upper panel are made of resin, and in that the closed cross-section shape that is configured by at least the outer front wall and the inner front wall is formed at a position at which the closed cross-section shape overlaps with a door belt line in an upper-lower direction of the vehicle body, when they are viewed from the vehicle width direction. a lower panel, including: a lower wall that forms a lower portion of a floor portion, and an outer front wall that is placed to extend upward from a vehicle body front end of the lower wall; and a lower wall that forms a lower portion of a floor portion, and an outer front wall that is placed to extend upward from a vehicle body front end of the lower wall; and an upper panel, including: an upper wall (40; 44) that forms an upper portion of the floor portion opposite to the lower wall and also forms a closed cross-section shape extending in a front-back direction of the vehicle body, and an inner front wall that is placed to extend upward from the vehicle body front end of the upper wall (40; 44) and joined to the outer front wall and that forms a closed cross-section shape that is connected to the closed cross-section shape extending in the front-back direction of the vehicle body and extends in a vehicle width direction while including both of left and right ends at an upper portion of the outer front wall, an upper wall (40; 44) that forms an upper portion of the floor portion opposite to the lower wall and also forms a closed cross-section shape extending in a front-back direction of the vehicle body, and an inner front wall that is placed to extend upward from the vehicle body front end of the upper wall (40; 44) and joined to the outer front wall and that forms a closed cross-section shape that is connected to the closed cross-section shape extending in the front-back direction of the vehicle body and extends in a vehicle width direction while including both of left and right ends at an upper portion of the outer front wall, the vehicle body structure being characterized in that the lower panel and the upper panel are made of resin, and in that the closed cross-section shape that is configured by at least the outer front wall and the inner front wall is formed at a position at which the closed cross-section shape overlaps with a door belt line in an upper-lower direction of the vehicle body, when they are viewed from the vehicle width direction.