To provide a garbage decomposing apparatus in which the apparatus itself is structured in compactly, the transportation handling time of garbage is saved and an odorless state is kept during the treatment of the garbage.

The garbage decomposing apparatus is provided with a casing 1 and a 1st and a 2nd cylindrical partition for dividing the casing 1 into a 1st treating tank 4, a 2nd treating tank 5 and a 3rd treating tank 6. A proper quantity of bacteria beds 11 where bacteria capable of decomposing the garbage inhabits is existed inside the 1st treating tank 4 and the 2nd treating tank 5. The garbage finely crushed by a compact apparatus capable of being installed under a sink is introduced directly into the decomposing apparatus to save the transportation handling. The odorless state is kept under the treatment of the garbage and malodor is not released.