Grape fruit quality can be deteriorated with leaf chlorosis caused by magnesium (Mg) deficiency during fruit coloring season in several grapevine varieties. The occurrence of leaf chlorosis and soil Mg states for four grapevine varieties (Campbell Early, Muscat bailey A (MBA), Sheridan, and Kyoho) in the vineyards of Gyeongsan and Youngcheon were surveyed. The relationships between leaf chlorosis and fruit qualities were also investigated. Leaf chlorosis was more widely found and the symptom was stronger in Campbell Early in comparison to the other varieties. Sugar content and Hunter values (L, a, b) of grape fruit were significantly lower in the trees of chlorosis when compare to healthy grapevine trees. Soil Mg contents in the vineyards where leaf chlorosis was found were lower than the optimum level for grapevine. Also Mg content in the petioles of chlorosis grapevines was significantly lower than healthy grapevines. Application of Mg through foliar spray and soil fertigation was quite effective in correcting deficiencies of Mg in grapevine. Proper management of soil Mg availability and K/Mg ratio is strongly recommended to prevent Mg deficiency in grapevine.