Device and method for correcting crt focus

PURPOSE: A CRT focus correcting device and a method thereof are provided to correct the focuses of R/G/B CRTs individually for correcting the focus per position of a screen precisely, thereby reducing the number of lens and simplifying the curvature shape of the lens. CONSTITUTION: A CRT focus correcting device includes a memory(411) for storing focus correcting data for respective R/G/B CRTs(407-409) per screen position. The focus correcting data includes focus correcting data respectively synchronized by horizontal and vertical synchronizing signals. A control part(410) reads out the focus correcting data according to horizontal and vertical synchronizing signals input from an image signal processing part(406). The read focus correcting data is output to an R/G/B focus correcting signal generating part(413). The focus correcting signals generated by the R/G/B focus correcting signal generating part are applied to R/G/B focus coils(407a-409a) for correcting the CRT focus.