Concept mapping activities have been used to enhance critical thinking skills as an essential competency for 21st century learners. However, little information has been provided about the relationship between different concept mapping activities and critical thinking skills. This study aimed to examine the effects of the fill-in-the-map activity and the construct-the-map activity on critical thinking skill development. 43 participants were recruited from the course, research seminar, in the department of English at a high school in Taiwan. There were two sections of the course in the same semester. Class A was randomly designated as the fill-in-the-map group and Class B as the construct-the-map group. The collected data included critical thinking survey scores, and interviews. The critical thinking survey scores collected from the two groups were analyzed using a multivariate analysis of variance to examine the difference in critical thinking skill development between the two groups. The multivariate results suggested that different concept mapping activities would produce different learning outcomes. The construct-the-map group significantly obtained higher scores than the fill-in-the-map concept mapping group in the critical thinking skills: inference, interpretation, analysis, evaluation, explanation. The interviews were analyzed to account for why the construct-the-map activity was more effective than the fill-in-the-map activity in developing students' inference, interpretation, analysis, evaluation, explanation skills. Suggestions and implications are proposed to develop critical thinking skills through concept mapping activities.