Provided is a method for monomerizing an MMP 7 aggregate. An MMP 7 monomerization method comprising treating an MMP 7 aggregate with a buffer solution including a low concentration of a monovalent cation chloride (such as sodium chloride potassium chloride etc.) or with said buffer solution not including a monovalent cation chloride. An MMP 7 preparation method incorporating said monomerization method and a (pharmaceutical) composition containing MMP 7 dissolved in said buffer solution. When preparing a (pharmaceutical) composition containing a low concentration of MMP 7 said buffer solution is used with a sugar alcohol or sugar added.
