We performed an exploratory thoracoscopy for a suspected diaphragm injury caused by a blunt-force chest trauma. A male patient in his fifties involved in a traffic accident and was transported by ambulance to our hospital. Upon arrival, his vital signs were stable, however, he was diagnosed as having fractures of the right tibia and fibula, multiple rib fractures and a slight right hemothorax. The limb fracture was treated by emergency surgery and the chest trauma was managed by chest drainage. Since injury of the diaphragm by fragment of the right 10th rib was suspected with chest computed tomography(CT), an exploratory thoracoscopy was performed after orthopedic surgery, and a laceration of the diaphragm without herniation was successfully closed.