The present invention provides a method of producing a liposome encapsulating an ammine platinum complex. The method includes A) providing a water-soluble ammine platinum complex, platinum complex raw materials or the combination thereof B) providing a liposome, liposome raw materials or the combination and C) preparing a mixture of the water-soluble ammine platinum complex, platinum complex raw materials or the combination thereof and the liposome, liposome raw materials or the combination thereof and subjecting it to a liposome-forming/maintaining condition, wherein the salt of the platinum complex forms when the liposome is in a water-soluble form.
