System usage, the utilization of information technology(IT) by individuals, groups or organizations, is a core variable in IS research. Indeed, there is widespread agreement among researchers that system usage is the primary variable through which IT affects white collar performance because it is a requisite, albeit insufficient, for deriving the benefits of IT. Furthermore, system usage has a notable practical value for managers interested in evaluating the impact of IT. Despite the number of studies of targeted at explaining system usage, there are more areas which required for the verification of system usage. The purpose of this paper is to address, using the Technological Acceptance Model (TAM), the usage pattern of AHP toward the various task in group decision (GD). The result showed that, for the all of the task types, perceived usage (PU) has more effect than perceived ease-of-use(PEU) on the AHP usage. However, more researches are required to generalize the result of this study.