This paper presents a developed Air Hockey Robot system, comprising camera unit, processing unit, and arm unit. This system performs as (1) detecting position of an Air Hockey puck from images captured using a ceil camera, (2) generating a 2-axis robot arm trajectory and (3) controlling the arm in order to shoot the puck to an opponent human player. Thus, the processing unit needs to execute three processes, i.e., image processing, trajectory generation, and arm control process. In this paper, we pay the most attention to trajectory generation process for improving the robot offensive performance. We give the robot a skill as attacking a weak point of human vision mechanism with respect to trajectory generation of the robot arm when it shoots stationary puck. In other words, the human player needs to change gaze points between the robot hand and the moving puck because the human can observe any object finely only in their central field of view, corresponding to around a fovea in spite of their quite wide field of view. Thus, we intend to plan the arm trajectory generation and control the arm as more easily the human players has a mistake caused by a time delay occurring when the human players switch their gaze point. Verification experiments, of changing speed of the puck shot from the same arm trajectory as the human players' mistake is caused easily, have been conducted using the developed Air Hockey Robot system.