A wheelchair-bound passenger restraint device has a wheelchair retractor that rewinds one end portion of a wheelchair belt member in an extractable manner, a wheelchair buckle that can be fitted with a wheelchair tongue plate, a passenger retractor that rewinds one end portion of a passenger belt member in an extractable manner, a passenger buckle that can be fitted with a passenger tongue plate, a buckle sensor that detects that the wheelchair tongue plate has been fitted to the wheelchair buckle, and a passenger belt lock mechanism that is configured to be able to make a changeover between a locked state making the passenger belt member unextractable an unlocked state making the passenger belt member extractable, and that makes a changeover from the locked state to the unlocked state when it is detected that the wheelchair tongue plate has been fitted to the wheelchair buckle.