1. A software robot apparatus, including a processor, the software robot apparatus providing a cyberspace in which objects, including at least one software robot, and environmental factors exist, the software robot apparatus comprising: a sensor unit for detecting environmental information and occurrences of external events due to an interaction among the objects, and generating a sensor value; a state unit for changing a state value of a state related to the external events and internal events occurring in relation to the software robot from among predefined physical states, predefined perception states, and predefined emotion states, which correspond to the software robot; an episode memory unit for storing episodes representing a progress of learning according to an expression of a particular behavior, each of the episodes including an object related to the particular behavior, and one of emotion states and perception states having a state value changed when the software robot expresses the particular behavior; and a behavior unit for, when a current perception state or a current emotion state is identified as an unstable perception state based on a current perception state value or an unstable emotion state based on a current emotion state value, enabling the episode memory unit to detect an episode capable of changing the unstable perception state or emotion state into a normal state, determining a behavior and an object stored in the detected episode as a final behavior object, and expressing a behavior of the software robot with reference to the object corresponding to the final behavior object, wherein the episode memory unit detects an episode related to a behavior type of a behavior expressed by the software robot from among the episodes, calculates a representative variance based on the variance stored in the detected episode and a generated state variance corresponding to the expressed behavior, and stores the representative variance as a variance of the detected episode, and wherein the respective episodes include one of the objects, one of predefined behaviors corresponding to the software robot, one of the predefined perception states and predefined emotion states, and a variance related to the state.