A curved belt conveyor (1) comprises a conveyor belt (2) with a hooking element (3) associated with an outer periphery (2a) of the conveyor belt (2); a plurality of pair of rollers (4) guiding the hooking element (3); a plurality of supporting elements (5) placed at the outer periphery (2a) of the conveyor belt (2) each for supporting at least one pair of rollers (4), a holding space (6) for the hooking element (3) of the conveyor belt (2) being defined among each pair of rollers (4) and the corresponding supporting element (5). A main roller (7) of one pair of rollers (4) is movable along a trajectory (T) extending along a longitudinal development of a corresponding main roller shaft (7a) between a releasing position, wherein the rollers (7, 8) are distant from each other defining a corresponding intermediate space (9) allowing the passage of the hooking element (3), and a retaining position, wherein the rollers (7, 8) are close to each other so that the defined corresponding intermediate space (9) does not allow the passage of the hooking element (3) of the conveyor belt (2) from the corresponding holding space (6) through the corresponding intermediate space (9).