A process for preparing Form A of (S)-5-methoxy-2-[[(4-methoxy-3,5-dimethyl-2-pyridinyl)-methyl]sulfinyl]-1H-benzimidazole magnesium dihydrate comprising crystallising or recrystallising crude (S)-5-methoxy-2-[[(4-methoxy-3,5-dimethyl-2-pyridinyl)-methyl]sulfinyl]-1H-benzimidazole magnesium dihydrate in the presence of ethyl acetate.(S)-5-메톡시-2-[[(4-메톡시-3,5-디메틸-2-피리딘일)-메틸]설피닐]-1H-벤즈이미다졸 마그네슘 2수화물의 형태 A의 제조방법, (S)-5-메톡시-2-[[(4-메톡시-3,5-디메틸-2-피리딘일)-메틸]설피닐]-1H-벤즈이미다졸 마그네슘 2수화물의 형태 A의 제조에 유용한 다양한 중간체의 제조방법, 및 5-메톡시-2-[[(4-메톡시-3,5-디메틸-2-피리딘일)-메틸]티오]-1H-벤즈이미다졸의 신규의 결정다형 형태 II.