A double-reeved lifting device for a lifting machinery, such as for example a crane, comprising two reeve blocks (3, 4), namely a lower reeve block secured to a lifting hook and an upper reeve block, wherein the two reeve blocks (3, 4) comprise reversible connection means adapted to be reversibly configured between: - a connected configuration in which the upper reeve block is connected to the lower reeve block so as to be able to accompany it in ascending/descending movements, and - a disconnected configuration in which the upper reeve block is disconnected from the lower reeve block so as to be able to remain hanging above the lower reeve block which could perform descending/ascending movements without the upper reeve block, wherein the connected configuration and the disconnected configuration respectively correspond to a double-reeved configuration and to a simple-reeved configuration, or vice versa, of the double-reeved lifting device, wherein the reversible connection means comprise a locking mechanism mounted on one of the two reeve blocks (3, 4), and a complementary locking structure mounted on the other one of the two reeve blocks (3, 4) and adapted to cooperate with the locking mechanism; said double-reeved lifting device being characterized in that the complementary locking structure comprises a set forming a striker having at least one striker orifice, and the locking mechanism comprises a bolt mounted slidably movable along a spindle along a main axis and comprising at least one locking finger, wherein the bolt is also pivotally movable around the spindle and the main axis between: - a locking state, applied in the connected configuration, with the locking finger inside the considered striker orifice, and - an unlocking state, applied in the disconnected configuration, with the locking finger out of the considered striker orifice so as to enable a relative approach and a relative distancing between the two reeve blocks (3, 4), and wherein the locking mechanism and the complementary locking structure comprise respective guide elements (57, 58, 570, 580, 68) cooperating together so as to convert a relative approach and a relative distancing between the two reeve blocks (3, 4) into concomitant slidings and rotations of the bolt. - a connected configuration in which the upper reeve block is connected to the lower reeve block so as to be able to accompany it in ascending/descending movements, and - a disconnected configuration in which the upper reeve block is disconnected from the lower reeve block so as to be able to remain hanging above the lower reeve block which could perform descending/ascending movements without the upper reeve block, wherein the connected configuration and the disconnected configuration respectively correspond to a double-reeved configuration and to a simple-reeved configuration, or vice versa, of the double-reeved lifting device, wherein the reversible connection means comprise a locking mechanism mounted on one of the two reeve blocks (3, 4), and a complementary locking structure mounted on the other one of the two reeve blocks (3, 4) and adapted to cooperate with the locking mechanism; said double-reeved lifting device being characterized in that the complementary locking structure comprises a set forming a striker having at least one striker orifice, and the locking mechanism comprises a bolt mounted slidably movable along a spindle along a main axis and comprising at least one locking finger, wherein the bolt is also pivotally movable around the spindle and the main axis between: - a locking state, applied in the connected configuration, with the locking finger inside the considered striker orifice, and - an unlocking state, applied in the disconnected configuration, with the locking finger out of the considered striker orifice so as to enable a relative approach and a relative distancing between the two reeve blocks (3, 4), - a locking state, applied in the connected configuration, with the locking finger inside the considered striker orifice, and - an unlocking state, applied in the disconnected configuration, with the locking finger out of the considered striker orifice so as to enable a relative approach and a relative distancing between the two reeve blocks (3, 4), and wherein the locking mechanism and the complementary locking structure comprise respective guide elements (57, 58, 570, 580, 68) cooperating together so as to convert a relative approach and a relative distancing between the two reeve blocks (3, 4) into concomitant slidings and rotations of the bolt.