Objectives : The purpose of this study is to investigate the effect of oral health education conducted by a dental hygienist in order to provide some information on intensive oral health education to elementary school students. Methods : Subjects were the students of J and M elementary schools in Seoul from October 28 to November 16, 2011. Oral health education was provided by a dental hygienist, and then they took the PHP test again to verify the effect of the oral health education. Results : Concerning changes in PHP scores after the oral health education, the scores of the students dropped from 2.34 in the pretest to 1.85 in the posttest(p<.001). As to changes in PHP scores by grade after the oral health education, the third graders and sixth graders got 2.40 and 1.36, respectively. Regarding satisfaction level with the oral health education, they got 4.07 out of five points. Among the items of satisfaction with the oral health education by grade, there were significant gaps in a change of toothbrushing method(p<.001) and a change of dietary control(p<.001) by grade. Conclusions : The finding of the study showed that both the third and sixth graders had less score in the PHP test and credibility to the effectiveness of the oral health education by the dental hygienist.