The successful use of digital textbooks (DTs) in schools requires the development of various teaching and learning methods that are appropriate for DTs. However, recent DT studies have focused mainly on the implementation of DT features and formats. The objective of this study was to investigate a problem-based learning instructional model appropriate to DTs and to present the experimental results using the problem-based DT to demonstrate its educational effectiveness. Two learning-achievements tests were conducted to analyze the learning experience and effectiveness of the problem-based DT after it had been used in a high school for a certain period. The experimental results indicated that the students who used the DT, especially lower-level students, exhibited improved problem-solving ability and demonstrated a better practical understanding of the subject than students who used printed textbooks.