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There are two main objectives for this research paper. First is to develop and find an efficiency of mathematics multimedia lessons. Second is to compare a learning achievement between before and after studying. Also, a sample group using for this research is twenty seven of 5^th primary students in Setsatian School for the Deaf, Bangkok from Purposive Sampling Method. As well, tools used for this research are testing exercises before study, testing exercises during study, testing exercises after study, questionnaires for content experts, and questionnaires for technique experts. As a result for this research, these multimedia lessons have efficiency at 84.58/83.07 that is over than estimate as 80/80. Furthermore, a learning achievement after study is higher than before one having .05 in statistical significance value. In conclusion, these mathematics multimedia lessons are efficient enough. They can be used for 5^th primary deaf students to study mathematics so well.