Provided is a method of manufacturing diesel fuel, including: fractionating in a first fractionator a synthetic oil obtained by Fisher-Tropsch synthesis into at least two fractions of a middle fraction, and a wax fraction containing a wax component heavier than the middle fraction; hydroisomerizing the middle fraction by bringing the 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 compound; fractionating in a second fractionator a mixture of the hydroisomerized middle fraction and the hydrocracked wax fraction into at least two fractions including a kerosene fraction and a gas oil fraction; and mixing the at least two fractions at a predetermined blend ratio to produce a diesel fuel having a kinematic viscosity at 30° C. of 2.5 mm2/s or more and a pour point of −7.5° C. or less.