A tablet dividing device is provided which can be compactly mounted in a tablet cassette mounting area of a drug dividing and packaging machine, so has excellent practicality, etc. A rotation transmission shaft (40) is provided which passes vertically through a box body (31). By placing the box body (31) on a base unit (13) of a tablet feeder mounted in a drug dividing and packaging machine, the lower end (43) of the rotation transmission shaft (40) is linked to the base unit (13) so as to be capable of transmitting rotation and a tablet guide mechanism (60) is linked to a cut tablet piece receiving unit (15) of the base unit (13). Furthermore, through rotation of a rotor (21), the tablet cassette (20) dispenses randomly contained tablets by dropping one at a time； by placing the tablet cassette (20) on the box body (31), the upper end (41) of the rotation transmission shaft (40) is linked to the rotor (21) so as to be capable of transmitting rotation and the tablet guide mechanism (60) is linked to a tablet dispensing unit (23) of the tablet cassette (20).
