A system comprising a sample processing device, a reaction container which has a plurality of reaction sites and can be placed in the sample processing device, and a dispenser tip for dispensing a solution into the reaction sites of the reaction container, the sample processing device comprising: a nozzle mechanism with a nozzle wherein the dispenser tip is attachable to and removable from the nozzle, and a drive control unit for controlling the nozzle mechanism, characterised in that the system further comprises: a magnetic tip attachable to and removable from the nozzle and comprising a magnetic substance for generating a magnetic field that allows magnetic beads to be migrated among the plurality of reaction sites in the reaction container, and a magnetic tip cover, wherein the nozzle comprises an apical end onto which the dispenser tip and the magnetic tip are mountable and a middle region which has a larger diameter than the apical end and to which the magnetic tip cover is attachable, wherein the sample processing device comprises a cover-removing mechanism adapted to remove the magnetic tip cover from the nozzle and retain the magnetic tip cover while the apical end of the magnetic tip cover has been inserted into the reaction site, and wherein the cover-removing mechanism comprises an upper retainer plate and a lower retainer plate opposed to each other with an interval therebetween, so as to sandwich a fringe region of the magnetic tip cover, and a notch region provided on one side surface of the upper retainer plate and the lower retainer plate a nozzle mechanism with a nozzle wherein the dispenser tip is attachable to and removable from the nozzle, and a drive control unit for controlling the nozzle mechanism, characterised in that the system further comprises: a magnetic tip attachable to and removable from the nozzle and comprising a magnetic substance for generating a magnetic field that allows magnetic beads to be migrated among the plurality of reaction sites in the reaction container, and a magnetic tip cover, wherein the nozzle comprises an apical end onto which the dispenser tip and the magnetic tip are mountable and a middle region which has a larger diameter than the apical end and to which the magnetic tip cover is attachable, a magnetic tip attachable to and removable from the nozzle and comprising a magnetic substance for generating a magnetic field that allows magnetic beads to be migrated among the plurality of reaction sites in the reaction container, and a magnetic tip cover, wherein the nozzle comprises an apical end onto which the dispenser tip and the magnetic tip are mountable and a middle region which has a larger diameter than the apical end and to which the magnetic tip cover is attachable, wherein the sample processing device comprises a cover-removing mechanism adapted to remove the magnetic tip cover from the nozzle and retain the magnetic tip cover while the apical end of the magnetic tip cover has been inserted into the reaction site, and wherein the cover-removing mechanism comprises an upper retainer plate and a lower retainer plate opposed to each other with an interval therebetween, so as to sandwich a fringe region of the magnetic tip cover, and a notch region provided on one side surface of the upper retainer plate and the lower retainer plate