A cancelling drive member includes a biasing cam portion having a first biasing contact portion and a second biasing contact portion formed therein. A deflectable spring member that biases the cancelling drive member forward is provided. If the cancelling drive member rotates, an elastic pressure portion of the deflectable spring member is brought into contact with the first biasing contact portion. Thus, a forward biasing force and a returning force for rotation are effectively given from the deflectable spring member to the cancelling drive member.