The present invention relates to a garbage treating appa ratus and. more particularly. to a garbage treating apparatus which is suitable for reducing garbage. such as vegetables dispensed from the home. by mixing the garbage with aerobic fungi and fermenting the garbage to an aerobic fungus and by decomposing the garbage to water and carbon dioxide gas. Recently. more attention has been given to garbage treat ing apparatus. because the garbage is decomposed by such apparatus. in large part. to water and carbon dioxide gas by the work of a bacteria. Also. the garbage is reduced sub stantially in weight to only about one-tenth of original weight of the garbage. A further advantage results from the fact that only a soil-form product and light dust remains. and these elements can be reused as compost. As one kind of a garbage treating apparatus for compost ing garbage through fermentation. there is a fermenting reactor which is disposed on its side. i.e. with its longitudinal axis horizontal. and into which garbage is introduced at one end. By operating a garbage agitating means provided in the fermenting reactor. the garbage is agitated and transferred to the other end thereof. Between the one end and the other end of the fermenting reactor. the garbage is decomposed through the Working of bacteria and compost is produced. One example of this type of conventional garbage treating apparatus is disclosed in Japanese patent laid-open publica tion No. 288953611988. In the above stated conventional garbage treating apparatus. the fermentation is performed by mixing the newly introduced garbage into the compost left over in the fermenting reactor. The compost includes a large number of bacteria and the garbage is decomposed by the working of the bacteria. In the conventional garbage treating apparatus of this type. where the fermenting reactor is disposed on its side. since the garbage is always introduced from the one end of the fermenting reactor and the compost generated by the fermentation is taken out from the other end of the fermenting reactor. it is possible to carry out a continuous fermentation operation. On the other hand. a garbage treating apparatus where a fermenting reactor is disposed upright with a vertical ori entation is disclosed in. for example. Japanese patent laid open publication No. 262.159/1994. In the garbage treating apparatus used in a home. it is necessary for the apparatus to have the following important factors. Namely. the garbage treating apparatus itself should have a low cost and provide low cost operation. and it should have a compact size. a high cleanness. a high hygiene. an odorless structure. and a good handling operation. In the garbage treating apparatus where the garbage is conveyed in the lateral direction. a continuous fermentation operation of the garbage is carried out. However. since the rotating shaft of the garbage agitating means is disposed in a horizontal direction. the torque of the motor which drives the shaft is large and the cost of the apparatus becomes high. On the other hand. in the garbage treating apparatus where the fermenting reactor is disposed upright with a vertical orientation. there are advantages in that a compact size apparatus can be obtained and the torque of the motor which drives the agitating means can be small because the rotating shaft therefor extends in the vertical direction. However. in such an upright garbage treating apparatus. there is a problem in that it is di?icult to mix the garbag