A self-cancelling mechanism is mounted on a steering column of a vehicle, is used for a turn-signal device signalling a change of a running direction of the vehicle and switches off turn-signal lamps by a returning rotation of a steering wheel. A ratchet is pivotally supported to a bracket pivoted to the steering column and is operated by a driver, and a cancelling cam body is arranged between the ratchet and the steering shaft. The ratchet is rotatable from its neutral position against the bracket up to a pair of rotation positions and is forced to the neutral position by an elastic member so that, even if the ratchet is suddenly returned back to the neutral position by the rotation of the steeling shaft in an anticancelling direction, striking noise does not occur.