PURPOSE: To facilitate automation of focus adjustment by quantizing focus measurement of a video image of a television receiver.

CONSTITUTION: The reception of the television receiver 12 is executed so as to display a test pattern required for focus adjustment onto a cathode ray tube 12a. A photoelectric conversion circuit 14 receives a emitted luminance of a scanning line of the test pattern displayed on the cathode ray tube 12a to output a photoelectric conversion signal Sa corresponding to the light quantity of the emitted luminance and to give it to a latch device 16. A focus adjustment volume 12b of the television receiver 12 is adjusted to allow the latch device 16 to latch a maximum voltage Sv of the photoelectric conversion signal Sa and it is displayed by a voltmeter 18 to set a maximum value.