The Japanese manufacturing industry is facing a shortage of new employees and an aging workforce due to the declining birthrate and aging population. In addition, the manufacturing industry needs new employees who can learn independently and cooperatively, and possess knowledge and skills in manufacturing. Project-based learning (PBL) is a learning method that allows independent and cooperative learning. Students who learned this method at the Tokyo University of Science in 2019 formed a small group and acquired not only technical skills in the manufacturing field but also interpersonal skills through communication and discussion with group members. However, the impact of COVID-19 in 2020 made it difficult to conduct face-to-face classes, making it was necessary to conduct online classes. As such, online education has attracted attention, as its allows learners and instructors to connect via the Internet and conduct classes remotely. However, in online learning, communication among learners may be insufficient. This study aims to encouraged students to share information by providing them with different information on how to improve their assembly skills and by giving them opportunities to communicate. It specifically investigates the effect of online PBL on the development of students in the manufacturing industry and examines the effect of PBL by introducing the LEGO block assembly training. With repeated assembly trainings, students improved their LEGO assembly skills and created assembly manuals for anyone to complete the task within a standard timeframe. The results show that students who are given different information and encouraged to communicate under online PBL improve their assembly skills more effectively than other students.