An image processing device and method that enable suppression of a reduction in coding efficiency. The image processing device dequantizes quantized data generated through decoding, using a default quantization matrix having a same size as a block size that is a unit of processing in which dequantization is performed, when in a copy mode in which a quantization matrix is copied, quantization matrix reference data identifying a reference destination of the quantization matrix matches quantization matrix identification data identifying the quantization matrix. The device and method can be applied to an image processing device.