In recent years, interventional radiology (IR) which is a medical procedure has been attracting considerable attention. Since this surgical method is less invasive, but doctors are exposed to strong radiation in the case under CT-guidance. In order to overcome this problem, we developed remote-controlled IR assistance robot. As a research topic, automated needle puncturing by the robot is focused on. However, currently the robot cannot obtain CT image in real time. So, the robot cannot obtain the form of needle based on CT image and cannot control state of needle accurately. On the other hands, we aim that the robot moves automatically for restraining a bend of needle. As the first step for this, the method to estimate a form of needle by using a force sensor information is proposed in this paper. If a form of the needle is displayed in user interface, it become easy for doctors to remove a bend of the needle during surgery with remote-controlled IR assistance robot. Additionally, we conducts the experiment to confirm effectiveness of proposed method.