Recently, an ionic decision-maker (IDM) was developed to efficiently process information by using nanoionic phenomena within Nafion polymer electrolytes. Whereas a Nafion-IDM is able to solve multi-armed bandit problem (MBP), it has an inherent drawback that is unsuitable for high integration: it requires an insertion of Pt/C-nanograins dispersion film to the electrode/Nafion interface in order to increase the effective electrode/electrolyte interface area, otherwise such electrode/Nafion interface resistance is very high due to a low effective interface area. In this study, we apply a graphene oxide (GO) membrane as a proton conducting electrolyte of the IDM. The Pt/GO low-resistance interface, which is attributed to the large contact area between small GO flakes and electrodes, enables a simple structure that does not require an insertion layer. In addition to that, a GO-IDM enabled very simple fabrication, it can solve MBPs with good performance comparable to a Nafion-IDM due to the high stability of GO. A GO-IDM is advantageous for achieving highly-integrated and flexible AI devices.