To provide a communication device by which a user can have a continuous and natural conversation by updating certainty factor as needed corresponding to ambient information detected from a sensor or the like and conversation contents in-between a conversation opponent.

The communication device is composed of a distributed sensor information DB 111, which stores sensor information from a sensor input part 101 by making it correspond to sensor type information and attributes, a distributed environmental action processing part 102, which executes recognition processing based on the sensor information stored in the distributed sensor information DB 111, a certainty factor imparting part 103, which imparts the certainty factor corresponding to the recognition results of the distributed environmental action processing part 102, and a distributed environmental action DB 110 which stores the recognition results of the distributed environmental action processing part 102 and the certainty factor imparted by the certainty factor imparting part 103 by making them correspond to the sensor information of the distributed sensor information DB 111.