PROBLEM TO BE SOLVED: To provide a method for production of vegetable oil cake and an adjustment method for potassium hydroxide (KOH) protein solubility of vegetable oil cake which can improve productivity and prevent increased cost by shortening the time for adjustment of conditions of manufacture to obtain the vegetable oil cake with desired KOH protein solubility.SOLUTION: A method for production of vegetable oil cake comprises: a desolventizing step of desolventizing extraction cake under water-adding and heating conditions； a step of measuring a value of a brightness axis, which is calculated from tristimulus values of XYZ color system of the oil cake during or after the desolventizing step, or the values of from red axis to green axis； and a step of adjusting the KOH protein solubility of the oil cake by adjusting a processing condition of the desolventizing step based on the value of a brightness axis or the values of from red axis to green axis having been measured.
