The purpose of this study is to examine how students' writing skills are improved by peer feedback in lesson practice. In lessons, students were first asked to write an introduction of "a power resource instead of fossil fuel" by using a mind map. Then, students exchanged their opinions about their writings in order to make them become aware of errors in grammar, expressions, and sentence structures in small group work activities. Through those activities, comparisons of first drafts done by each student with his/her revised draft after peer feedback were conducted. Findings of this study reveal that students tended to write more expressively in their drafts after feedback compared with their first drafts. Therefore, this study concludes that students' writing skills to write coherent sentences have been improved through peer feedback.