The aim of this paper is to analyse two varieties of Hateruma dialect, in order to describe diatopic and diachronic changes. Hateruma dialect belongs to the Yaeyama dialect group, and is spoken on Hateruma island as well as in the Shiraho village of Ishigaki island. The paper aims to compare the two varieties through an acoustic phonetic analysis, setting as a parameter the vowel space. It also carries out a comparative analysis between the varieties spoken by different generations, in order to show diachronic changes. The acoustic phonetic approach allows us to gain a deeper understanding of the Hateruma dialect vowel system.