The purpose of this study is to investigate how fifth and sixth graders recognize average and to find out suggestions for teaching/learning methods of average by examining which difference there is depending on the way of the word problem presentation. To solve these study questions, With the way of the word problem presentation set up as experimental treatment experiment was conducted to analyze these. In conclusion, since students who did not learn the regular course of average values had various informal concepts already, it is needed to consider handling more various concepts of average in order to enable students to expand flexible thoughts. And informal concepts of average students showed were the same or similar to types of formalized concepts and had logicality and propriety in their own way. Compared with fifth graders, sixth graders showed a wide difference in informal concepts of average depending on the way of the word problem presentation.