A video encoding apparatus and method and a video decoding apparatus and method are provided. The video encoding apparatus includes a base layer encoding unit generating a base layer bitstream including a quantization level of video data and a base quantization parameter corresponding to a base bit-depth, an enhancement layer encoding unit generating an enhancement layer bitstream including a refined quantization parameter for refining the difference between an extended bit-depth and the base bit-depth, and a bitstream combining unit combining the base layer bitstream and the enhancement layer bitstream to generate the scalable bitstream. The video decoding apparatus includes a base layer decoding unit decoding a base layer bitstream including a quantization level of video data and a base quantization parameter corresponding to a base bit-depth in a received bitstream to obtain a base restoration image, an enhancement layer decoding unit decoding an enhancement layer bitstream including a refined quantization parameter for refining the difference between an extended bit-depth and the base bit-depth in the received bitstream, and a bit-depth restoration unit obtaining an extended restoration image corresponding to an extended bit-depth by using the decoded quantization level, the decoded base quantization parameter, and the decoded refined quantization parameter.