To reduce a burden on a user in editing tree structure data with a text editor. When a selection range is designated on an edit screen, a node selection unit of a tree structure data editing device selects one or more node IDs in the tree structure data, based on the position of the selection range. When a paste target for the selection range is designated on the edit screen, a connection target determination unit determines a connection target node ID in the tree structure data, based on the position of the paste target. A tree structure data editing unit edits the tree structure data such that the node or nodes identified by the one or more node IDs is/are connected to the node identified by the connection target node ID. A conversion unit convers the tree structure data edited by the tree structure data editing unit into text data. A display control unit updates the edit screen displayed, based on the text data converted by the conversion unit.