The purpose of this study were to examine the effect of elementary children`s general characteristics and physical activity on self-efficacy by investigating their general characteristics and the realities of their physical activity. The subjects were 139 boys and girls selected from 5th and 6th graders attending elementary school in Inchon as of 2003.. The measurement instrument consisted of Youth Health Survey(1997) on physical activity used by the American youth health organization and the modified and supplemented scale on children`s physical activity. Data analysis was conducted through such statistical techniques as t-test, one-way ANOVA using SPSS 11.5. As a result, the following results were obtained: In terms of the frequency of physical activity, it was found that elementary children on average engaged in physical activity in each event once or twice a week And it was found that female children had the higher score in MET2 than the male counterparts but that male children had the higher score in MET3, MET5, MET8. The male children showed the higher score on physical activity than the female counterparts, and it was found that elementary children`s physical activity scores had a significant effect on their self-efficacy (whole domain and self-efficacy(intellectual domain. The male children had a positive attitude towards physical activity, Whereas the female children had a nagatvie attitude. It was found that there was a significant difference according to the school year. That is, the 5th graders showed the higher scores than the 6th counterparts. in conclusion it was found that elementary children`s physical activity had a significant effect xi self-efficacy(socio-emotional domain).