Actuation device for a control cable for a bicycle gearshift, comprising: - a casing, configured for fixing to bicycle handlebars, - a cable-winding bush, on which the control cable is wound and which is angularly mobile in the casing about a main axis of the device, - a rotation pin of the cable-winding bush arranged along the main axis, - an indexing bush coaxial to the cable-winding bush and associated with it to removably hold the cable-winding bush in predetermined angular positions, angularly spaced apart from each other by predetermined indexing angles (α), - a manoeuvring mechanism, operative on the cable-winding bush to rotate it in a first angular direction about the main axis of the device, to obtain an upward gearshifting, wherein between the cable-winding bush and the indexing bush it is provided a coupling with a predetermined circumferential clearance corresponding to a predetermined gearshifting extra-stroke angle (β), wherein the manoeuvring mechanism comprises a first gearshift lever, which is angularly mobile with respect to the casing about the main axis of the device, in the first angular direction starting from a neutral position to obtain the upward gearshifting, wherein the first gearshift lever acts on the cable-winding bush so as to: - impose a first rotation of the cable-winding bush with respect to the casing and to the indexing bush in the first angular direction by the predetermined gearshifting extra-stroke angle (β), - impose a second rotation of the cable-winding bush with respect to the casing, together with the indexing bush, in the first angular direction by the respective predetermined indexing angle (α), and - allow a third rotation of the cable-winding bush with respect to the casing and to the indexing bush in a second angular direction opposite to the first angular direction by the predetermined gearshifting extra-stroke angle (β), wherein the manoeuvring mechanism comprises a second gearshift lever, which acts on the indexing bush to allow a rotation thereof, together with the cable-winding bush, in the second angular direction about the main axis of the device, so as to obtain a downward gearshifting. - a casing, configured for fixing to bicycle handlebars, - a cable-winding bush, on which the control cable is wound and which is angularly mobile in the casing about a main axis of the device, - a rotation pin of the cable-winding bush arranged along the main axis, - an indexing bush coaxial to the cable-winding bush and associated with it to removably hold the cable-winding bush in predetermined angular positions, angularly spaced apart from each other by predetermined indexing angles (α), - a manoeuvring mechanism, operative on the cable-winding bush to rotate it in a first angular direction about the main axis of the device, to obtain an upward gearshifting, - impose a first rotation of the cable-winding bush with respect to the casing and to the indexing bush in the first angular direction by the predetermined gearshifting extra-stroke angle (β), - impose a second rotation of the cable-winding bush with respect to the casing, together with the indexing bush, in the first angular direction by the respective predetermined indexing angle (α), and - allow a third rotation of the cable-winding bush with respect to the casing and to the indexing bush in a second angular direction opposite to the first angular direction by the predetermined gearshifting extra-stroke angle (β),