In the Kishi and Arida valleys of Wakayama Prefecture, it is common to find farmhouses with a compacted earthen room which is partly furnished with a raised floor area. This raised floored area is called the agarito in these districts. This agarito is used in everyday life as a space for receiving guests, and also used, on the occasions of ceremonies, as an extension area of the zashiki , the Japanese formal style guest room. This paper aims to trace the formation process of the agarito and to clarify the reasons for its formation. The agarito does not have a long history. It first appeared in upper class houses during the Meiji era. During the Taisho era, it found its way into middle-class farmhouses and a house plan with the agarito incorporated was employed for new houses. The main factors for the development of the agarito were the local tradition of having the daidokoro space expanded into the earthen floor room, and the traditional local practice of using the daidokoro space for receiving guests in addition to its normal use as a family gathering place.