Coriolis sensor of a Coriolis measuring device designed to measure a mass flow or a density of a medium flowing through at least a measuring tube of the Coriolis measuring device, said sensor comprising: at least a measuring tube with an inlet and an outlet, which is designed to conduct the medium between the inlet and the outlet; at least an exciter, which is designed to excite the at least one measuring tube; at least two sensors, which are designed to measure, respectively, the vibrations of at least one measuring tube; wherein at least an exciter and/or at least a sensor each have a coil unit each with at least a coil (14.1), and each have a magnet device, wherein the magnet device and the coil unit are mobile in relation to one another, wherein the sensor has a carrier body, which is designed to hold the at least one measuring tube, wherein the magnet device has a holder for magnets (15.3) and at least a first magnet group (15.1) with at least one magnet and at least a second magnet group (15.2) with at least a magnet, wherein the holder has a U-shape with a first leg (15.31) and a second leg (15.32), and a base (15.33) connecting the legs, wherein the holder surrounds the coil unit in such a way that the first leg is arranged on a first side of the coil unit (14.01) in relation to a coil cross-section, and the second leg is arranged on a second side of the coil unit (14.02), wherein the first magnet group is held on the first side of the coil unit by the holder, and the second magnet group is held on the second side of the coil unit by the holder, wherein the holder has a cavity (15.4) in the area of the legs, wherein the cavities are designed to receive the magnet groups, wherein the cavities are formed, respectively, by a cavity wall (15.5), wherein the cavity wall each has at least a first opening (15.51) to receive a magnet group, characterized in that each magnet group has two magnets (15.6) and at least a magnetically conductive closing unit (15.7), wherein the magnetic fields of the two magnets are oriented in an opposite manner, and the closing unit is designed to guide and connect field lines of the magnetic fields of the two magnets, wherein the magnets are in mechanical contact with the closing unit, wherein magnetic fields of opposing magnets of different magnet groups are oriented in the same direction. at least a measuring tube with an inlet and an outlet, which is designed to conduct the medium between the inlet and the outlet; at least an exciter, which is designed to excite the at least one measuring tube; at least two sensors, which are designed to measure, respectively, the vibrations of at least one measuring tube; wherein at least an exciter and/or at least a sensor each have a coil unit each with at least a coil (14.1), and each have a magnet device, wherein the magnet device and the coil unit are mobile in relation to one another, wherein the sensor has a carrier body, which is designed to hold the at least one measuring tube, wherein the magnet device has a holder for magnets (15.3) and at least a first magnet group (15.1) with at least one magnet and at least a second magnet group (15.2) with at least a magnet, wherein the holder has a U-shape with a first leg (15.31) and a second leg (15.32), and a base (15.33) connecting the legs, wherein the holder surrounds the coil unit in such a way that the first leg is arranged on a first side of the coil unit (14.01) in relation to a coil cross-section, and the second leg is arranged on a second side of the coil unit (14.02), wherein the first magnet group is held on the first side of the coil unit by the holder, and the second magnet group is held on the second side of the coil unit by the holder, wherein the holder has a cavity (15.4) in the area of the legs, wherein the cavities are designed to receive the magnet groups, wherein the cavities are formed, respectively, by a cavity wall (15.5), wherein the cavity wall each has at least a first opening (15.51) to receive a magnet group, characterized in that each magnet group has two magnets (15.6) and at least a magnetically conductive closing unit (15.7), wherein the magnetic fields of the two magnets are oriented in an opposite manner, and the closing unit is designed to guide and connect field lines of the magnetic fields of the two magnets, wherein the magnets are in mechanical contact with the closing unit, wherein magnetic fields of opposing magnets of different magnet groups are oriented in the same direction.