To provide a drainage mechanism of a sink, which hardly deteriorates a radially-slit cover.

This drainage mechanism of the sink comprises: the radially-slit cover 1 which is provided in the upper part of a garbage receiving basket 8 of a drain inlet 7 of the sink, which becomes narrower toward a central side, and the base part of which is equipped with a plurality of tongue pieces 5 with a hole part 4; a ring body 15 which is provided with a plurality of storage parts 17 for storing a chemical agent 16 for inhibiting the formation of a biofilm or a chemical agent with an antibacterial action, and which is detachably installed on the front side of the radially-split cover 1 in the state of making each of the storage parts 17 inserted into each of the hole parts toward the backside of the radially-split cover from the front side thereof; a cartridge 32 with a vent hole 35, which is detachably installed on the backside of the radially-split cover 1; and the chemical agent 31 which is stored in the cartridge 32, and which has the odor eliminating action of eliminating an abnormal odor via the vent hole 35 by adsorption. The size of the storage part 17 is set to be suitable for the closing of the hole part 4.