According to the extended-mind thesis, our mental states and processes can extend beyond our body into the environment. This paper introduces and defends Rowland’s proposal for the conditions the satisfaction of which provides a sufficient reason to regard the external states and processes occurring outside of our bodies as being cognitive or mental. According to the principle which we might call “mental-state internalism,” a being’s mental states can never extend beyond its own boundaries. When the external states and processes satisfy the Rowland’s conditions for the extension of mentality, it also seems to follow that the subjects of such states also extend beyond their skin. This is the thesis of extended-self. I examine Olson’s and Baker’s objections to the extended-self thesis, and try to elucidate the notion of extended-self in terms of ‘narrative self.’ The extended-self thesis, thus understood, challenges the traditional conception of self which views a self as a sort of substantial thing that owns our various mental activity or characteristics. According to the conception of narrative self, a self is understood as the center of narrative gravity to the stories which have been told both to ourselves and others, and told both by ourselves and others, consisting of a certain set of ongoing goals, projects, and commitments.