Abstract
Modal realism is an ontological claim according to which there exist many possible worlds just like our actual world. Since it is so hard to believe, modal realism has only a few advocates. However, it is well known that alternative theories have serious problems. It is one of the central issues of metaphysics to find a persuasive way to reject modal realism. In this paper, I will suggest that it could be accomplished with help of metaontology-one of the topics of metaphysics which has recently discussed intensely. I will show how we could argue against modal realism from the metaontological point of view.