This study analyzed the evaluations of instructors and experts on flipped learning-based engineering in order to suggest improvement strategies. This study was conducted with 8 engineering courses which participated in the flipped learning course development project of C university from 2017-2018. As a result of the analysis, the instructors and experts pointed out that the pre-learning was not performed and checked effectively. In this regard, the instructors suggested the students' burden of pre-learning, the lack of understanding about flipped learning, and the experts suggested the lack of instructional strategies to facilitate pre-learning. In addition, the instructors and the experts pointed out that the courses were still instructor-centered. The instructors evaluated that they operated the instructor-led course by themselves. In addition, the experts suggested that there was not enough instructional strategies to activate the learner-centered activities. The number of the students and the lecture room environment that were not appropriate for the learner- centered class were the evaluation opinions of both the instructors and the experts. In addition, the professor suggested the lack of understanding and preparation of the flipped learning of the instructors and the learner as the main opinion, and the experts pointed out that the online learning system and classroom was not linked for pre-learning, classroom learning, and the post-learning. Based on these results, suggestions for improvement of flip learning based engineering course were suggested.