Occupant protecting device and air bag device for rear-end collision mounted on vehicle

A vehicle (20) includes an air bag device (30) for an occupant seated in a rearmost seat (27). The air bag device (30) includes an air bag (31), which is accommodated at the rear end portion of the roof (21) of the vehicle (20) in a folded state, and an inflator (32), which supplies gas to the air bag (31). The air bag (31) is unfolded downward to be inflated between the rearmost seat (27) and a rear window glass (25a). The air bag device (30) has several functions to effectively protect an occupant seated in the rearmost seat (27), such as a function to apply a predetermined tension to the inflated air bag (31), a function to properly restrict the thickness of the air bag (31), and a function to properly control the unfolding direction of the air bag (31).