The present invention provides a gas oil composition for use in a diesel engine containing an FT synthetic base oil and having a sulfur content of 5 ppm by mass or less, an oxygen content of 100 ppm by mass or less, a bulk modulus of 1250 MPa or greater and 1450 MPa or less, a saybolt color of +22 or greater, a lubricity of 400 μm or less, an initial boiling point of 140° C. or higher and an end point of 380° C. or lower in distillation characteristics, wherein: (1) the cetane number in a fraction range of lower than 200° C. is 20 or greater and less than 40; (2) the cetane number in a fraction range of 200° C. or higher and lower than 280° C. is 30 or greater and less than 60; and (3) the cetane number in a fraction range of 280° C. or higher is 50 or greater.