PURPOSE: To enable the automatic compilation of an index of a page of contents based on the data on compositions in the text by a method wherein the composition data on a titled line selected and stored in a temporary memory means and the page-number data thereon detected by a detecting means are paired to be printed.

CONSTITUTION: When a composition in a paragraph A1, which is a major classification category, is inputted, a key K1 representing a major classification is operated to make a composition buffer 7 store a control code α. A composition in a paragraph A1 is inputted subsequently, and when an input for one line is ended, a new line start instruction key is operated to make the composition buffer 7 store a new line start control code. Furthermore a composition in a paragraph X1 is inputted and stored in th composition buffer 7. When the input of a text is ended by these operations, a printing instruction is given by a key K2. By a printing operation thus instructed, the composition data stored in the composition buffer 7 are fetched by one line to a line output buffer 61 of RAM6 and supplied to a printing control unit 8, and a document is formed in a printing device 9. When an index for contents is compiled, the key K1 is operated for setting an automatic contents-compilation mode, and thereafter the key K2 is operated to give a printing instruction.