Disclosed are a method and a device for encoding a video by using a data unit of a hierarchical structure, and a method and a device for decoding the same. According to one embodiment of the present invention, a video encoding device: encodes a picture that constitutes a video on the basis of a data unit of a hierarchical structure; determines a context model that is used for entropy coding of a symbol on the basis of hierarchical information of a data unit to which a symbol for the encoded picture belongs; and entropy encodes the symbol by using the determined context model.