The primary purpose of this study is to verify the positive relation between the ability to recognize game situations and skill level of ball game players in the field experimental setting with the real game space. And the secondary purpose is to give some experimental data about decision-making of ball game players. In order to fulfill these purposes, static situations in rugby football were examined. The experimental task was to recognize the weak points in defensive disposition in game situations from the attacker's point of view. The number of weak points in one defensive disposition varied from zero to two. After subjects searched into each game situation during four seconds, they were required to answer the following questions : 1) Where is the weak point to attack? 2) How will you attack there? Three skill levels of players(1st=1st squard players in a university club; 2nd=2nd/3rd squard players in a university club; and B=beginners in a university rugby class) were chosen as subject groups. Each consisted of such positions like scrum half, stand off, center, and full back, two players in each position. The major results are summarized as follows: 1. The significant positive trend that the players of higher skill level displayed the better experimental result in terms of both correct responses (number of weak points recognized correctly) and errors of commission was obtained. This is a finding that supports some similar findings of the previous literature in field experimental situations. In order to confirm further this positive relation, similar field experimental study on dynamic game situations should be expected. 2. For number of attacking plays corresponding correctly to one weak point replied correctly (question 2), B was significantly inferior to 1st and 2nd, 1st and 2nd the same. As a result, B seemed to possess the inferior system of association between game situations and plays than the cases of 1st and 2nd, but the speed of decision-making and contents of plays selected are indispensable to determine the quality of ball game players. Hence, further study along the line should be expected.