An air-bag type passenger restraining device for a motor vehicle comprises a vehicle collision sensor which issues a first instruction signal when detecting a vehicle collision; an air-bag which is located in front of a seat of the vehicle and instantly inflated when receiving a second instruction signal; an air-bag retreating device which instantly retreats the air-bag in a direction away from the seat when receiving a third instruction signal; and a control unit for producing the second and third instruction signals upon receiving the first instruction signal. The control unit issues the third instruction signal for starting the air-bag retreating device after the air-bag is inflated to such a degree as to effect an initial restraint to a passenger on the seat due to issuance of the second instruction signal therefrom.