An image encoding/decoding method and an apparatus thereof are provided. The decoding method includes: determining a coding unit by splitting an image; determining a transform unit in the coding unit; determining whether to decode residual data of the transform unit according to a transform skip mode; obtaining a significant subgroup flag about a subgroup in the transform unit; based on the significant subgroup flag indicating that the subgroup includes at least one non-zero significant coefficient and scanning information about coefficients of the subgroup, obtaining a first bin about a significant coefficient flag, a sign flag, a first flag, and a parity flag of a coefficient of a scan position; obtaining the residual data including a coefficient in the subgroup based on the base level and a remainder of an absolute value excluding the base level; and obtaining a reconstruction block of the coding unit, based on the residual data.