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.
