2'-Deoxy-3',5'-di-O-alkylcarbonyl-5-fluorouridine derivatives possessing strong anti-tumor activity with weak toxicity and represented by the general formula: ##STR1## wherein R stands for an alkyl group, an alkoxy group or a halogen atom, m for zero or an integer of 1-3, and n for an integer of 1-14, with the proviso that when m is 2 or 3, R's may be the same or different and that when m is 2 and the adjacent two R's are alkoxy groups, the two alkyl moieties of the alkoxy groups may be combined to form together with the two adjacent oxa bridging members an alkylenedioxy group as a whole. These derivatives are prepared by acylating a 2'-deoxy-3',5'-di-O-alkylcarbonyl-5-fluorouridine with corresponding benzoyl halides and are useful as active ingredients for anti-tumor agents, especially for oral administration.