We report a case of pulmonary thromboembolism, in which obstruction of the right subclavian vein, also called Paget-von Schroetter syndrome, was detected. The patient was a 39-year-old man (a scaffold constructor). He lost consciousness at work, and was admitted as an emergency case to our hospital. He had noticed gradually worsening dyspnea for 1 month. Chest radiography showed Westmark's sign in the lungs and enlarged hilar vascular markings on both sides. Pulmonary perfusion scintigraphy confirmed multiple flow defects. Upper and lower limb venography disclosed interruption of the right subclavian vein, leading to a diagnosis of pulmonary thromboembolism secondary to upper limb vein thrombosis. In patients who have pulmonary thromboembolism without an apparent underlying disease, the lifestyle and work habits should be considered and the possibility of subclavian vein thrombosis should be kept in mind.