Industrial plant (1; 50) for milling leathers comprising: - a support framework (2; 51) suitable to rest on a reference surface of an industrial factory; - a rotatable drum (3; 52) coupled with said support framework (2; 51) and comprising a hollow body (4; 53) suitable to receive the leathers to be treated, defining a symmetry axis around which said hollow body (4; 53) is put in rotation by motorization means associated with said support framework (2; 51) and having a through opening (5; 54) at which a shaped shutter is revolvingly coupled with said hollow body (4; 53) and cooperates with actuation means suitable to place it between a first position, in which said shaped shutter tightly closes said through opening (5; 54), and a second position in which said shaped shutter at least partly opens said through opening (5; 54) for loading into the inner volume of said hollow body (4; 53) of said leathers to be treated and/or discharging from said inner volume of said hollow body (4; 53) of said treated leathers; - a motorized conveyor belt (8; 57), at least partly facing and underlying said hollow body (4; 53) and which: • receives said treated leathers, coming by fall from said hollow body (4; 53), when said shaped shutter takes said second position; • conveys said treated leathers away from said hollow body (4; 53), characterized in that, in transversal section made in the longitudinal development direction of said conveyor belt (8; 57), said conveyor belt (8; 57) presents a curved profile having concavity facing towards said hollow body (4; 53) at least in the linear portion of said conveyor belt (8; 57) on which said treated leathers fall, coming out from said hollow body (4; 53) of said rotatable drum (3; 52) through said through opening (5; 54). - a support framework (2; 51) suitable to rest on a reference surface of an industrial factory; - a rotatable drum (3; 52) coupled with said support framework (2; 51) and comprising a hollow body (4; 53) suitable to receive the leathers to be treated, defining a symmetry axis around which said hollow body (4; 53) is put in rotation by motorization means associated with said support framework (2; 51) and having a through opening (5; 54) at which a shaped shutter is revolvingly coupled with said hollow body (4; 53) and cooperates with actuation means suitable to place it between a first position, in which said shaped shutter tightly closes said through opening (5; 54), and a second position in which said shaped shutter at least partly opens said through opening (5; 54) for loading into the inner volume of said hollow body (4; 53) of said leathers to be treated and/or discharging from said inner volume of said hollow body (4; 53) of said treated leathers; - a motorized conveyor belt (8; 57), at least partly facing and underlying said hollow body (4; 53) and which: • receives said treated leathers, coming by fall from said hollow body (4; 53), when said shaped shutter takes said second position; • conveys said treated leathers away from said hollow body (4; 53), characterized in that, in transversal section made in the longitudinal development direction of said conveyor belt (8; 57), said conveyor belt (8; 57) presents a curved profile having concavity facing towards said hollow body (4; 53) at least in the linear portion of said conveyor belt (8; 57) on which said treated leathers fall, coming out from said hollow body (4; 53) of said rotatable drum (3; 52) through said through opening (5; 54). • receives said treated leathers, coming by fall from said hollow body (4; 53), when said shaped shutter takes said second position; • conveys said treated leathers away from said hollow body (4; 53), characterized in that, in transversal section made in the longitudinal development direction of said conveyor belt (8; 57), said conveyor belt (8; 57) presents a curved profile having concavity facing towards said hollow body (4; 53) at least in the linear portion of said conveyor belt (8; 57) on which said treated leathers fall, coming out from said hollow body (4; 53) of said rotatable drum (3; 52) through said through opening (5; 54).