A shock absorbing apparatus for an aircraft seat that attenuates shock to passengers and crews includes; an airbag 11 being expanded in a plate shape in a state of less than maximum expansion; an upper flat plate 12 arranged on one side of the airbag 11; a lower flat plate 13 arranged on another side of the airbag 11; a gas supply device 15 for supplying a gas to the airbag 11; and a detector sending a signal to activate the gas supply device 15 by a preset condition. The shock is absorbed by expanding the airbag 11 before the shock is applied to the passenger.