The purpose of study was to develop a Mathematics learning tool based on a realistic, valid and effective mathematical approach to improve the ability of fraction concepts. This is part of the research & development which has three stages, and they are: (1) Preliminary research, (2) Prototyping, including (a) designing, (b) formative evaluation, and (c) prototype revision, and (3) Assessment. The instruments were test of the fraction concept ability, and questionnaire of motivation. The analysis of data was the inferential and descriptive statistics. The results is that realistic mathematical learning tools were feasible to apply and were easy to use, easy to understand and very helpful for the learning process. The learning tool could strengthen students' motivation. The conclusion was that as for the ability of understanding fraction concepts, students who use realistic mathematical learning tools is higher than students who learn conventionally. Thus, a real-time mathematics-learning tool can replace conventional learning.