The Korean Ministry of Education, Science, and Technology has investigated a great deal of budgets and efforts in development and diffusion of digital textbooks for last 15 years. Most of the digital textbooks, 16 out of 18(88%) are developed for elementary school students. For last a few years, development and application test of digital textbooks have been held in total 132 elementary schools. Also, there have been a great amount of related researches published so far almost 150 studies. There, however, were few studies done to evaluate those digital textbooks with teachers and students in terms of the suitability in actual elementary school classroom. Therefore, the purpose of this study is to evaluate and suggest improvement strategies of these digital textbook for instructional suitability. The researcher selected 36 elementary school teachers and students who had at least 1-2 years of digital textbook application experiences in actual classrooms. The teachers and students were from the two digital textbook experiment schools appointed by The Korean Ministry of Education, Science, and Technology. These two schools are located in Gwangju Metropolitan City and Jeon-nam province. The selected digital textbooks for evaluation were Social Studies and Sciences in grade, 4th, 5th, and 6th. Teachers and students evaluated digital textbooks based on their experience with them for last one or two years by using two types of evaluation tools(checklist and open-ended questions). The researchers also interviewed teachers with the open-ended question. The data collection was occurred for three months from October to December, 2011. The results of this study indicated that teachers were not likely much satisfied with the digital textbooks in terms of instructional suitability in elementary school instructional environment. The average of the total evaluation score was 2.8 (teachers 2.71, students 2.96) in 5 points scale. It means only about 59% in percentile. This result implied those digital textbook had not given much influences in improvement of class instruction. In addition, the researcher surveyed the major problems and improvement strategies of them. The results show that teachers and students indicated the similar problems even though the difference of their ages and professional understanding levels of instructional settings. Also there were a number of the problems pointed out often regardless the evaluation sections and elements. Those are that digital textbooks were poor in three aspects such as assisting students' individual differences, motivating higher level thinking, and difference from ordinary textbooks. The study provided a summery of the major problems and design alternatives suggested.