There has been a lot of research on the focus particle even on the perspective of quantification, truth-conditional value, implicature, etc. This paper attempts to translate the findings in terms of grammaticalization. This paper addresses grammaticalization of even from a lexical adverb meaning ``uniformly, smoothly,`` to a scalar focus particle and modal particle, invoking the mechanisms of grammaticalization such as subjectification, intersubjectification, modality, mirativity, etc. It is argued on the basis of subjectification that even decodes the speaker`s evaluation and belief of the endpoint on a scale. Intersubjectification accounts for the fact that the endpoint on a scale depends on the mutual belief of the speaker and the addressee in the discourse world. Even also designates the attitude of the speaker such as counterexpectation, surprise, unexpected information toward the proposition as a modal particle.