To provide a method for producing a diluent oil as a diluent oil for 2-cycle engine oil, which has low odor and a high flash point even if using kerosene/light oil fraction, improves air/smoke ventilation performance or the like, can blend high viscosity lubricant component excellent in lubricity, and satisfies improved miscibility with gasoline.

There is provided the method of producing the diluent oil used for 2-cycle engine oil, wherein: a kerosene/light oil fraction, having ≥90 vol.% saturated content, 0-30 ppm sulfur content, 0 vol.% aromatic content, ≥65°C aniline point, 270-400°C end point by Engler distillation, ≥60 cetane index, ≥70°C flash point and 2.0-9.0 kinetic viscosity at 40°C, is subjected to production process including at least one process selected from a Fischer Tropsch synthesis process, a hydrocracking process of wax-containing component, and a hydrogenation purifying process of components obtained from those processes.