Mass measuring apparatus associable with an automatic processing machine (50; 60) for measuring mass (m a) of articles (100; 200) or parts thereof, processed by said automatic processing machine that comprises at least one movement device (30; 130) provided with seats (33, 34; 133) for housing and moving said articles (100; 200), comprising: - transferring and gripping means arranged to remove an article (100; 200) or a part thereof from a respective seat (33; 133) of said movement device (30; 130), hold said article (100, 200) or part thereof in a measuring position (A; D3) and then reinsert said article (100; 200) or part thereof into the respective seat (33; 133), said transferring and gripping means comprising at least one gripping element (3; 7) adapted to hold said article (100; 200) or part thereof in said measuring position (A; D3); - actuator means (13; 6) arranged to operate with an actuating signal on said gripping element (3; 7), in particular for making said gripping element (3; 7) vibrating alone at a specific resonance frequency (f 0); characterized in that it further comprises: - sensor means configured for measuring a vibration response signal, said gripping element (3; 7) vibrating and supporting said article (100; 200) or part thereof in said measuring position (A; D3); - a processing unit connected to said sensor means and arranged to receive said vibration response signal and to control said actuator means (13; 6) in order to: - generate an actuating signal of said actuator means (13; 6) able to make said gripping element (3; 7) supporting said article (100; 200) or part thereof vibrate at an operating resonance frequency (f m) and then calculate a mass (m a) of said article (100; 200) or part thereof by comparing said operating resonance frequency (f m) with said specific resonance frequency (f 0) of said gripping element (3; 7); or alternatively - generate an actuating signal of said actuator means (13; 6) able to make said gripping element (3; 7) supporting said article (100; 200) or part thereof vibrate at said specific resonance frequency (f 0) of said gripping element (3; 7) and calculate a mass (m a) of said article (100; 200) or part thereof by measuring an operating phase difference (Δφ m) between said actuating signal of said actuator means (13; 6) and said vibration response signal detected by said sensor means. - transferring and gripping means arranged to remove an article (100; 200) or a part thereof from a respective seat (33; 133) of said movement device (30; 130), hold said article (100, 200) or part thereof in a measuring position (A; D3) and then reinsert said article (100; 200) or part thereof into the respective seat (33; 133), said transferring and gripping means comprising at least one gripping element (3; 7) adapted to hold said article (100; 200) or part thereof in said measuring position (A; D3); - actuator means (13; 6) arranged to operate with an actuating signal on said gripping element (3; 7), in particular for making said gripping element (3; 7) vibrating alone at a specific resonance frequency (f 0); - sensor means configured for measuring a vibration response signal, said gripping element (3; 7) vibrating and supporting said article (100; 200) or part thereof in said measuring position (A; D3); - a processing unit connected to said sensor means and arranged to receive said vibration response signal and to control said actuator means (13; 6) in order to: - generate an actuating signal of said actuator means (13; 6) able to make said gripping element (3; 7) supporting said article (100; 200) or part thereof vibrate at an operating resonance frequency (f m) and then calculate a mass (m a) of said article (100; 200) or part thereof by comparing said operating resonance frequency (f m) with said specific resonance frequency (f 0) of said gripping element (3; 7); or alternatively - generate an actuating signal of said actuator means (13; 6) able to make said gripping element (3; 7) supporting said article (100; 200) or part thereof vibrate at said specific resonance frequency (f 0) of said gripping element (3; 7) and calculate a mass (m a) of said article (100; 200) or part thereof by measuring an operating phase difference (Δφ m) between said actuating signal of said actuator means (13; 6) and said vibration response signal detected by said sensor means. - generate an actuating signal of said actuator means (13; 6) able to make said gripping element (3; 7) supporting said article (100; 200) or part thereof vibrate at an operating resonance frequency (f m) and then calculate a mass (m a) of said article (100; 200) or part thereof by comparing said operating resonance frequency (f m) with said specific resonance frequency (f 0) of said gripping element (3; 7); or alternatively - generate an actuating signal of said actuator means (13; 6) able to make said gripping element (3; 7) supporting said article (100; 200) or part thereof vibrate at said specific resonance frequency (f 0) of said gripping element (3; 7) and calculate a mass (m a) of said article (100; 200) or part thereof by measuring an operating phase difference (Δφ m) between said actuating signal of said actuator means (13; 6) and said vibration response signal detected by said sensor means.