The purpose of this study is, based upon referent informational influence, to examine the group context that generates of group polarization (GP) for varying the outgroup position. Prototype is prescribed by the meta-contrast ratio (MCR), in case the ingroup position is similar to outgroup one, the prototype of it polarizes to differentiate it with outgroup. GP is to generate through the conformity with this polarized prototype. Then, it was hypothesized that GP generates based upon referent informational influence when ingroup position is similar to outgroup one, it does not when difference exits between both positions regardless of the direction of them. It was established three conditions (similar to outgroup, different from outgroup but same direction and different direction). At the result of discussion after presentation of three conditions, it supported the hypothesis. The examination regarding the relationship between attitude shift neglecting conformity and the conformity by referent informational influence showed both conformity to the prototype and attitude shift in the similar condition, it was suggested that GP could be explained by referent informational influence.