An environment identifying apparatus (400) is adapted to be mounted in a robot apparatus that moves in an identifiable unique environment in which a plurality of landmarks are located so as to identify the current environment by means of a plurality of registered environments. The environment identifying apparatus comprises an environment map building section (402) for recognizing the landmarks in the current environment, computing the movement/state quantity of the robot apparatus itself and building an environment map of the current environment containing information on the positions of the landmarks in the current environment on the basis of the landmarks and the movement/state quantity, an environment map storage section (403) having a data base of registered environment maps containing positional information on the landmarks and environment IDs, an environment identifying section (404) for identifying the current environment on the basis of the degree of similarity between the environment map of the current environment and each of the registered environment maps and an environment exploring section (405) for exploring a new environment.