Examples of how to manage classes of Project Based Learning (PBL) in the field of mechanical engineering are proposed from the viewpoint of efficient combination between lecture-style lessons and practical training. The classes of PBL have already been introduced into the engineering educational program, and they are sometimes managed by Professors invited from industries. Though PBL classes are recognized to be effective for motivation of students, little common understanding has been established on the relation between expert knowledge obtained through lecture-style lessons and the topics presented in PBL classes. All professors are required to re-establish a sheared awareness of teaching expert knowledge for engineering students in practical use. For this purpose, several examples of ideal points treated in PBL classes are proposed in this article.