The present disclosure relates to an image coding device and method, and an image decoding device and method for enabling the code amount of a chrominance signal in an image to be controlled. A chrominance signal quantization unit determines a luminance signal quantization parameter and a chrominance signal quantization parameter in units of CU by use of a luminance signal quantization parameter, a chrominance signal quantization parameter, and ChromaQPOffset from a rate control unit, and supplies the determined luminance signal quantization parameter and chrominance signal quantization parameter to a quantization unit. The chrominance signal quantization unit calculates a predictive quantization parameter predQP based on the quantization parameters of adjacent CUs. The chrominance signal quantization unit calculates deltaQP and ΔQPC based on the determined luminance signal quantization parameter and chrominance signal quantization parameter and the calculated predictive quantization parameter predQP. The chrominance signal quantization unit supplies the calculated deltaQP, ΔQPC, and ChromaQPOffset to a lossless coding unit. The present disclosure can be applied to an image processing device, for example.