The purpose of this study was to develop a letter type rubric as a learning method for elementary school students to learn science writing easily and efficiently. For this study, five topics in science textbooks were chosen and modified in everyday life situation. The rubric evaluation criteria were composed of four steps. Two classes of 4th grade of an elementary school in Seoul were selected for applying the developed rubric. The experimental group consisted of 25 students and control group consisted of 28 students. The letter type rubric was treated to experimental group. The results showed that there was a significant difference between two groups in the science writing ability after application. From the survey results, we could conclude that the rubric helps elementary school students to develop the science writing ability and confidence in writing.