A tablet cassette for a tablet feeder comprising: a tablet container configured to contain a number of tablets (104, 108) and including a bottom wall portion having an outlet port formed therein and a peripheral wall portion; a rotor including an axis portion rotatably passing through the bottom wall portion of the tablet container and configured to rotate centering on the axis portion, wherein an upper surface of the rotor is shaped to cause the tablets to align; a plurality of partition portions radially extending from an outer peripheral portion of the rotor and circumferentially spaced at a given interval such that an annular gap defined between the rotor and the peripheral wall portion of the tablet container is partitioned at an equal pitch to form a plurality of tablet receiving portions; and a fall prevention mechanism including a readily deformable elastic member or flexible member disposed upwardly of the outlet port and at a position higher than the partition portions, and configured such that one or more extra tablets locating on or above one of the tablet receiving portions, which comes closest to the outlet port by rotation of the rotor, are pushed toward the rotor by means of a repulsive force generated by deformation of the elastic member or the flexible member when the one or more extra tablets abut on the elastic member or the flexible member, thereby to prevent the one or more extra tablets from falling down into the outlet port, characterized in that: the fall prevention mechanism includes an endless belt and a pair of pulleys (152, 152) operable to rotatably support the endless belt with a tensile force being applied to the endless belt; and the endless belt constitutes the elastic member or the flexible member. a tablet container configured to contain a number of tablets (104, 108) and including a bottom wall portion having an outlet port formed therein and a peripheral wall portion; a rotor including an axis portion rotatably passing through the bottom wall portion of the tablet container and configured to rotate centering on the axis portion, wherein an upper surface of the rotor is shaped to cause the tablets to align; a plurality of partition portions radially extending from an outer peripheral portion of the rotor and circumferentially spaced at a given interval such that an annular gap defined between the rotor and the peripheral wall portion of the tablet container is partitioned at an equal pitch to form a plurality of tablet receiving portions; and a fall prevention mechanism including a readily deformable elastic member or flexible member disposed upwardly of the outlet port and at a position higher than the partition portions, and configured such that one or more extra tablets locating on or above one of the tablet receiving portions, which comes closest to the outlet port by rotation of the rotor, are pushed toward the rotor by means of a repulsive force generated by deformation of the elastic member or the flexible member when the one or more extra tablets abut on the elastic member or the flexible member, thereby to prevent the one or more extra tablets from falling down into the outlet port, characterized in that: the fall prevention mechanism includes an endless belt and a pair of pulleys (152, 152) operable to rotatably support the endless belt with a tensile force being applied to the endless belt; and the endless belt constitutes the elastic member or the flexible member. the fall prevention mechanism includes an endless belt and a pair of pulleys (152, 152) operable to rotatably support the endless belt with a tensile force being applied to the endless belt; and the endless belt constitutes the elastic member or the flexible member.