This study was carried out to investigate relationship between yields and sugar contents in protected-film-cultivated melon (Cucumis melo) by different nitrogen and potassium fertilization levels. Melon plants, cv. Ales elite, were transplanted on April, 2005. As a result of analyzing soil chemical properties used in experiment, EC, organic matter, total nitrogen, Av. P2O5, K, Ca, and Mg were 1.19 dS m-1, 11.2 g kg-1, 0.4g kg-1, 104 mg kg-1, 0.4, 7.5, 1.2 cmol kg-1, respectively. The N-P-K levels of four different established were 11-4-14, 13-4-16, 15-4-18, and 17-4-20. At harvesting season (80 days after planting), we measured fruit yields and sugar contents in melon fruit using portable refractometer. Fruit yields of melon grown in different fertilization levels such as 11-4-14, 13-4-16, 15-4-18, and 17-4-20 were 3,526, 3,549, 3,019, 2,557 kg 10a-1, respectively. An excessive N-K application resulted in a decrease of yields due to prolonged vegetative growth. Also, Sugar contents in melon fruit harvested under different N-K supply, 11-4-14, 13-4-16, 15-4-18, and 17-4-20, were 13.8, 15.0, 15.0, and 16.0 obrix, respectively. High N-K supply, 17-4-20, promoted higher sugar accumulation in melon fruit. Considering the relationship between yield and sugar, value as marketable product is the best at 13-4-16 of N-P-K application. Key words : melon, yield, sugar content.