The purpose of this study is to develop a inquiry learning instrument and to evaluate the effec-tiveness of experiment in the concept-forming about mapping and interpretation of the geological map. Unfortunately no proper experimental instruments on the content of this study has been utilized in the current domestic Earth Science textbooks. In this study, the geological struc-ture models with 4 different dips were developed. In order to evaluate the effectiveness of the experiment, we prepared a test consisted of 10 problems and compared the test results performed by the control group who conducted the exper-iments along with regular class with another test results performed by comparative group who participated only regular class without experiment. The control group is consisted of 102 girls` high school students in Taegu area, and the comparative group is 104 students. The test results are as follow : i)The mean of the test results of the control group (XA) is 7.18, while that of comparative group(XB) is 6.38. ii)The difference of the test scores between two groups has been turned out to be highly significant at the 0.05 level of significance. (t = 3.270 at the criterion for significance, a=0.05 and the degree of freedom, df= 206). This suggest that the class learned by the experiment is more effective in the concept-forming of the making and interpretation of the geological map than the class only learned by lectures.