In respiratory diseases typified by lung cancer, biopsy in the lung using an endoscope is considered as effective for diagnosis. However, even skilled physicians are difficult to insert it. In order to simplify these biopsies, this paper presents a novel operation of a self-propelled catheter and its basic configuration for automatically reaching the target lung periphery. The proposed device consists of a flexible tube with an outer diameter of 2.6 mm, and both of the propulsion motion and steering motion are generated by the pneumatics. We verify the validity of the proposed methods through simple experiments by the developed prototype.