The disclosure presents an embroidery data processing device and a computer program product capable of creating a single unit of tree structure vector data by coupling plural pieces of independent tree structure vector data. A coupling node is added between nodes and of a tree structure vector data, and a vector data to for coupling nodes and, and a vector data to for coupling nodes and are created, and thereby a tree structure vector data is created. In a tree structure vector data, the node mutual direction is converted so that the node existing at the connecting position may be a root node, and a tree structure vector data is created, and this root node is coupled with the coupling node of the tree structure vector data, and a single tree structure vector data is created.