The objectives of this research are: 1) produce a valid and practical pocket book of building material based on realistic mathematical  education approach (RME), 2) know the potential effect that arises from developing pocket book of building material of flat side space, 3) knowing the student's response to pocket book material of building flat side space. Development of pocket book is done through two stages of priliminary stage (preparation) and formative evaluation stage. The results of this study show that pocket book wake up flat side space using RME approach that produced valid and practical. Valid is reflected from the revision after being validated by an expert based on content, constructs, and language. Based on the document analysis of the work result of the students during field test, showed the final test of learning using Pocket book with RME approach get very good category 43,75%, good 28,12%, enough 15,62%, and less 12,5%, data result the test is that the learning done shows a good potential effect. Based on analysis of student response result to pocket book developed for indicator of interest in pocket book obtained 86,09% student express strongly agree, material indicator 79,97% student agree and indicator from linguistic side 89,32% student strongly agree Keywords: Pocketbook, PMRI