Abstract: A handlebar shifter device for operating bicycle derailleur system includes a fixed piece connected to a bicycle handlebar and a recess defined in the end surface of the fixed piece for receiving a resilient member therein. A rotatable member is rotatably mounted to a tube of the fixed piece and an annular flange extends from an end surface of the rotatable member. A cable retaining hole is defined in the fixed piece for receiving a derailleur cable therein and a free end of the cable is fixed to the rotatably member. Two blocks extend from the rotatable member and a plate is mounted on the annular flange. Two protrusions extend from an outer periphery of the plate and respectively contacting two blocks on the rotatable member. A plurality of notches are defined in an outer periphery of one of the protrusions and an index peak of the resilient member is engaged with one of the notches.