Abstract: Arfak numerical system is uniquely categorized. It is because Arfak tribe uses base number 10 sub base 5. This study is focused on the numerical construction and the shift analysis of its own construction. This research used ethnography. The study was conducted in Hingk District, Arfak Regency, West Papua, Indonesia. The subjects of the study were Arfak residents consisted of ordinary people, tribe leaders and public figures. Based on the development of the culture, the society of Arfak has 3 types of numbers in Hatam language. The both types are the number of base 5, 10 and base 10 sub base 5. The outsider affects the type of number in Arfak culture. This influence caused the metamorphosis of numbers in Arfak cultures. The metamorphosis is seen in the change of base number 5 to base 10 sub-base 5.