Two field experiments were carried out at Agronomy Department Exp. Farm, Faculty of Agricultural, Assiut University, Assiut, Egypt 2010/2011 and 2011/2012 seasons to investigate the response of two sugar beet cultivars to nitrogen application level and time. A randomized complete block design (RCBD) using a split-plot arrangement with three replications was used. Two sugar beet cultivars were assigned to the main plots while, seven the nitrogen combination were randomly arranged in the sub-plots. The obtained results showed that the N fertilizer application level and time had a significant effect on the root and top fresh weights and yields of sugar beet plants. Increasing the N applied level up to 120 kg fed.^-1 decreased the sugar percentage and juice purity of roots. On the other hand, the early application of N at 30 days after planting using 90 kg N fed.^-1 splitting into three doses was ranked to be the best treatment for improving the root quality and increasing the root gross and extractable sugar yields. The purity of root juice that combined with a good sugar yield quality was obtained from applying the three equal doses of N fertilizer in compared with two equal doses. It can be concluded that the N applied level at three times of plant growth stages lead to raise the yield and quality of the tops and roots of sugar beet.