PURPOSE: To display a character pattern for convergence adjustment without any dedicated equipment by providing an on-screen output device for displaying various kinds of information in a monitor TV set on a screen and a microcomputer for controlling this output device inside the monitor TV set.

CONSTITUTION: An on-screen output device 2 and a microcomputer 1 are arranged inside the monitor TV set. The micrcomputer 1 receiving an instruction showing the executing of convergence adjustment from a control panel 3, judges the kind of convergence adjustment by receiving the designation of character display for convergence adjustment from the control panel 3, selects characters optimum for the convergence adjustment and calculates an optimum point on the screen for outputting the convergence control characters. Then, the characters for convergence adjustment are displayed on the on-screen character display device 2 and their display positions are designated.