Speech quality of VoIP (Voice over Internet Protocol) may potentially be degraded by transmission errors such as packet loss and delay that are basically inevitable in best-effort communications. This study newly proposes an error concealment technique for such degradation by taking account of both sender-based and receiver-based techniques. In the proposed technique, sender-based side information, which is required by the receiver-based technique, is transmitted by using steganography, so that its datagram is completely compatible with the conventional format of VoIP. From experimental results of objective evaluation, it is indicated that the proposed technique may potentially be useful for improvement of speech quality, compared with the conventional technique.