PURPOSE: To form and correct efficiently a control program, by corresponding the section of the control pogram with a sheet No. code, and managing an operation block No. belonging to each sheet No. by a sheet information table.

CONSTITUTION: A programmer PRG34 performs the program forming, correction and display of a controller and is connected to the controller via a tansmission interface adaptor DCG35. The programmer PRG34 comprises a central processing unit CPU1, a keyboard KB inputting data and a display CRT for the display of programs and the like. A part of the control program described with an operation specifying table and an operation sequence table is displayed on the CRT display as a control block diagram. The entire control block diagram is divided into some groups, each group is given with its identification number (called sheet No.), and each control block diagram is designated by this sheet No.