An image encoding/decoding method and apparatus are provided. The image decoding method performed by the image decoding apparatus, according to the present disclosure, may comprise the steps of: determining whether a color space transformation is applied to residual samples of a current block; determining quantization parameter of the current block on the basis of whether the color space transformation is applied; and determining a transformation coefficient of the current block on the basis of the quantization parameter. The step of determining the quantization parameter may be performed by limiting the range of an effective value of the quantization parameter such that a value of the quantization parameter has a value less than or equal to a predetermined upper value and greater than or equal to a predetermined lower value.