An image encoding/decoding method and apparatus are provided. An image decoding method performed by an image decoding apparatus comprises obtaining quantization mode information for a current block from a bitstream, determining whether a quantization matrix for the current block is constructed from a reference quantization matrix, based on the quantization mode information, and constructing the quantization matrix for the current block, based on a result of determination. When the quantization matrix for the current block is constructed from the reference quantization matrix, the quantization matrix for the current block may be constructed based on identification information of the reference quantization matrix. When the quantization matrix for the current block is not constructed from the reference quantization matrix, the quantization matrix for the current block may be constructed based on a value of the quantization matrix obtained from the bitstream. When the current block is an intra-predicted chroma block, the quantization matrix for the current block may be constructed only when a size of the current block is greater than 2×2.