There is disclosed an interface enabling easy implementation of processing on hierarchical data, and a method facilitating comprehension of the structure, meaning, and format of hierarchical data. There is also disclosed a data processing device including a user interface portion receiving data with tuples each a combination of data of different types, and lists each a series of data of a same type, display data obtained by converting the data, and an instruction requesting processing from a user, and presenting the display data, data managing portion managing the hierarchical data, display-data generating portion generating the display data from the hierarchical data, and analyzing portion implementing the processing. Data is presented in a table format having rows displaying level names and attribute names, respectively. The generating portion samples data of each level of hierarchical data to extract an amount possible to present, and converts the data format.