The purpose of this study was to investigate changes in geological contents knowledge and self-confidence before and after the geological field trips. Fifty seven undergraduate students at a national university of education participated in this study. The questionnaires were developed by the researcher to serve the purpose. Findings were as follows. First, before and after the geological field trip, there was no significant difference in changes of geological content knowledge (p<.05). However, participants` self-confidence about the geological field trip changed significantly (p<.01). Second, there were no significant differences in changes of both variables in terms of gender (p<.05). And in this study, participants were grouped into two: science track that selected science areas and non-science track with social study selected in the college scholastic ability test. There were also no significant differences in changes of geological contents knowledge and self-confidence in terms of science or non- science track (p<.05). Third, in terms of the geological content knowledge, 24 pre-service teachers showed an increase, 12 students unchanged, and the 21 participants decreased. In contrast, per participants` self-confidence about the geological field trip, fifty three students indicated an increase with only one participant unchanged, and three preservice teachers decreased on the score. Finally, after the geological field trip, participants` comments indicated that they could feel the mystery of nature with the mind of a great experience. As a result, data showed that pre-service teachers became interested in geology, and motivated more in learning geological area than ever.