A detachable-roof-equipped vehicle body structure includes a seal member provided in a roof opening section, and a soft top constructed to abut against the seal member. The seal member includes first and second seal units, and the soft top includes a flexible sheet for covering the roof opening section and a reinforcing member of higher rigidity than the sheet. The reinforcing member is abutted, from above, against both of the first and second seal units. The structure also includes a connecting bag part secured to the sheet, left and right side rails attached to the sheet, and a wire member inserted through the bag part and extending between the side rails. The wire member includes a small-diameter portion, and large-diameter portion each provided on a position spaced from a corresponding one of the side rails.