A method of and an apparatus for encoding and decoding using transformation bases of a yet higher efficiency. In a method for encoding an object signal in compliance with a transformation rule, a signal correlating to the object signal is obtained, and a transformation base that forms the transformation rule is derived based on a characteristic of the obtained reference signal. The object signal is transformed and encoded in compliance with the transformation rule based on the derived transformation base. Accordingly, the object signal is transformed in compliance with the transformation rule based on the transformation base derived from the characteristic of the reference signal. Since the reference signal is correlated to the object signal, the transformation base derived from the characteristic matches the feature of the object signal.