A scalable encoding apparatus capable of suppressing the quality degradation of a decoded signal without increasing the bit rate. In this apparatus, a core layer encoding part (101) and an extended layer encoding part (102) encode an input signal for each of audio frames. When a replacement determining part (103) determines that a degree to which the input signal changes between a preceding frame and a current frame is equal to or greater than a predetermined value or that a degree, to which the quality of the decoded signal is improved by an extended layer encoding process in the preceding frame, is equal to less than a predetermined level, a replacing part (105) replaces a part of an extended layer encoded data of the preceding frame by a core layer encoded data of the current frame. That is, a transmitting part (108) transmits, as a backup, the core layer encoded data of the current frame to a decoding end in advance.