Provided is a rocuronium preparation designed to reduce vascular pain to be induced. The rocuronium preparation contains rocuronium and a buffer solution, and has titratable acidity of 100 mEg or less. The buffer solution may be an acetate buffer solution, a citrate buffer solution, a formate buffer solution, a tartrate buffer solution, a phosphate buffer solution, a glycine-hydrochloric acid buffer solution, or a citric acid-phosphate buffer solution.