A data classification method and a device thereof for hierarchical multi-label classification are proposed. The data classification device includes an encoder configured to vectorize data, a decoder configured to receive the vectorized data from the encoder, and classification data stored in the decoder, wherein the decoder starts classification of the vectorized data on the basis of a first node in the classification data, allocates a plurality of nodes included in the classification data to the vectorized data, and forms partial layers based on the allocated nodes with respect to the vectorized data, and when terminal nodes or temporary nodes are allocated among the nodes, the decoder ends the allocation to the partial layers to which the terminal nodes or the temporary nodes are allocated and allocates final partial layers formed on the basis of the partial layers to the data.