The Seldinger technique is a well-established medical procedure to insert an indwelling device into blood vessel. Although the method is widely performed, various adverse effects due to the procedure have been reported. In order to improve safety, some hospitals originally compiled important reminders based on their experiences in an operation manual. The aim of our research is to provide evidences supporting failure behaviors with a mock system to promote awareness in clinical practice. This paper presents results of a newly developed test method to evaluate the possibility of perforation while inserting the dilator to the cervical vein after the guidewire placement. A tensile tester (AGI-250kN, Shimadzu Corp.) equipped with a load cell (SLBL-50N, Shimadzu Corp.) was utilized to measure the insertion force of a dilator to vein. The porcine vein was prepared to be aligned with 15mm and to be cut opened to expose the medial wall, and it was mounted on a custom-made device. A guidewire and a dilator were vertically suspended from the upper side of the tensile tester. During the dilator was approaching down to the vein through the guidewire at the constant velocity, the insertion force was measured and the tissue surface was observed simultaneously. The perforation force was examined in relation to the insertion angle from 15degrees to 60degrees. While veins were pressed only by a guidewire, perforation was not identified at all degrees. After inserting a dilator, veins were torn at 45degrees and at 60degrees more than 10N. It was suggested that vessel wall could be thinner and be torn by multiple insertion. It is concluded that the usage situation of a guidewire and a dilator was assessed objectively and the angle-load relationship was quantified. The test would be helpful to propose safe approach for patients.