Fifteen measurements of the vapour pressure and seven measurements of the saturated-liquid density for n-butane were obtained by means of a metal-bellows variable volumometer at T = (280 to 424) K. The mole fraction purity of the n-butane used in the measurements was 0.9997. The expanded uncertainties (k = 2) in temperature, pressure, and density measurements have been estimated to be less than 3 mK, less than 0.8 kPa, and 0.08%, respectively. Throughout the present measurements for n-butane, the vapour-pressure value and saturated-liquid density value at each temperature were determined as average value of the pressures on various volume of the bellows at the same temperature, and as the point of intersection between the isotherm and our vapour-pressure value, respectively. The expanded uncertainties (k = 2) in the present vapour-pressure data and saturated-liquid density data have also been estimated to be less than 1.1 kPa and 0.08%, respectively, except the uncertainty of the saturated-liquid density data at T = 424 K being 0.29% (0.83 kg · m−3). Based on the present measurements as input data, the Wagner-type vapour-pressure correlation and the saturated-liquid density correlation were also provided for the systematic comparisons between the present measurements and the literature data.