Disclosed is a method of manufacturing a diesel fuel base stock improved in low-temperature flowability, including: fractionating in a first fractionator a synthetic oil obtained by Fisher-Tropsch synthesis into at least two fractions of a first middle fraction containing a component having a boiling range corresponding to diesel fuel oil, and a wax fraction containing a wax component heavier than the first middle fraction; hydroisomerizing the first middle fraction by bringing the first middle fraction into contact with a hydroisomerizing catalyst to produce a hydroisomerized middle fraction; hydrocracking the wax fraction by bringing the wax fraction into contact with a hydrocracking catalyst to produce a wax-decomposition component; and fractionating in a second fractionator a mixture of the produced hydroisomerized middle fraction and the produced wax-decomposition component, wherein rectification conditions in the first fractionator and/or rectification conditions in the second fractionator are adjusted to selectively reduce an n-paraffin having 19 or more carbon atoms in a heavy component contained in the diesel fuel base stock. Furthermore, disclosed is a diesel fuel base stock obtained by the manufacturing method.