PURPOSE: To improve the precision of measurement and adjustment of color convergence by using a crosstalk coefficient to calculate the luminance level distribution of each color fluorescence based on the light intensity level distribution of each color component.

CONSTITUTION: A solid-state image pickup device 3 picks up the image of a display face of a color cathode-ray tube 1 through a filer 2 consisting of red, green, and blue filters to measure the light intensity distribution on all of the display face. A signal processor 6 performs prescribed signal processing based on respective chrominance signals and data read out from respective chrominance signal memories 5R, 5G, and 5B. That is, crosstalk coefficients indicating the light intensity levels in which red, green, and blue color fluorescence forming a white measuring pattern in the color cathode-ray tube 1 are measured as the other color components through the color filter 2 are preliminarily measured, and crosstalk coefficients are used to calculate the luminance level distributions based on light intensity level distributions of respective color components, which are measured through the filter 2, of the measuring pattern displayed on the color cathode-ray tube 1.