This vehicle-occupant's status detecting device is provided in a vehicle having a running-supporting device for supporting driving operations of a vehicle-occupant in the vehicle on moving. The vehicle-occupant's status detecting device includes: a biological data detecting device having a vibration-detecting sensor which detects biological data of the vehicle-occupant; and a detection-permitting device which permits, only when the running-supporting device is in operation, the biological data detecting device to detect the biological data.