Disclosed herein are a method, an apparatus and a storage medium for image encoding/decoding. For efficient image compression, efficient syntax is required. Pieces of information required for image decoding may be structurally or semantically associated with each other. Based on this association, whether signaling of one piece of information is to be performed may be determined based on another piece of information. Further, based on this association, the signaling order or priority of multiple pieces of information may be determined. Depending on this determination, based on the number of subpictures present in a picture in high-level syntax, the number of slices present in the picture may be selectively signaled.