A vehicle side structure includes a window, which has a window opening defined in a side wall of a vehicle and a window glass for covering the window opening, a curtain air bag device attached to a position above the window, and a bar-shaped member configured to partition the window opening into upper and lower sections when viewed along a lateral direction of the vehicle. In the vehicle side structure, the bar-shaped member is placed inside the window opening or at a position located, in a vehicle width direction, on an inner side of the window opening and also on an outer side of a fully inflated curtain air bag, and at least a part of the fully inflated curtain air bag expands to a region below the bar-shaped member.