PURPOSE: Provided are a mild hydrocracking apparatus using external material in the boiling range of middle distillates and a method for producing high quality middle distillates from a vacuum light oil hydrotreating apparatus. CONSTITUTION: The method includes the steps of: (a) passing a hydrocarbonaceous feedstock to a first hydroprocessing zone having one or more beds containing hydroprocessing catalyst; (b) passing the effluent of step (a) directly to a hot high pressure separator; (c) passing the vapor stream from step (b) after cooling and partial condensation to a hot hydrogen stripper containing at least one bed of hydrotreating catalyst; (d) passing the overhead vapor stream from the hot hydrogen stripper of step (c), after cooling and contacting with water, to a first cold high pressure separator; (e) passing the liquid stream from the hot hydrogen stripper of step (c) to a bed of hydroprocessing catalyst in the second reactor stage; (f) passing the overhead from the cold high pressure separator of step (d) to an amine absorber; (g) passing the separator bottoms of step (b) to a second reaction stage; (h) passing the vapor stream of step (g) after cooling to a second cold high-pressure separator; (i) passing the liquid effluent of step (g) after cooling to the cold high-pressure separator of step (h) to separate hydrogen and light hydrocarbonaceous gases from the liquid effluent; (j) passing the vapor stream from steps (h) and (i) after further cooling and separation of condensate, to the make-up hydrogen compressor; (k) passing the compressed hydrogen from the make-up hydrogen compressor to the primary reactor loop; and (l) passing the liquid effluent from steps (h) and (i) to the fractionation system.