The purpose of this study was to examine third graders’ multiplicative thinking levels and to analyse how they applied such thinking in solving proportional problems. As a result, many students revealed transitional thinking among the four kinds of thinking levels. This means that they had a difficulty in distinguishing multiplicative situations from additive ones and that they tended to think both additive and multiplicative. This study is expected to pay more attention to the multiplicative thinking in early grades and to provide instructional implications of teaching multiplication.