A webbing tension adjusting apparatus for use in a webbing retractor employed in a seatbelt system for a vehicle which is arranged such that one end of an occupant restraining webbing is secured to a door of the vehicle and such that it is possible for an occupant of the vehicle to be automatically secured by the webbing simply by closing the door. When the door is opened, a resilient member for winding up the webbing is disengaged from a takeup shaft by a clutch means, whereby the biasing force of the resilient member which has been applied to the takeup shaft is cancelled. There is therefore no possibility that the webbing which is being wound off from the webbing retractor in response to the door opening operation may rub strongly against the body of the occupant.