Flexible actuator which consists of a thrust wire and a linear motor realizes flexible arrangement of an actuator and an end-effector. Flexible actuator is able to transmit force sensation through a thrust wire. Thus, it is expected to be utilized in haptic motion systems. However, thre is an unignorable error between the generated force of the actuators and the actual force which is transmitted through the thrust wire. This is because of the disturbances such as the friction, and the mechanical play of a thrust wire. In this paper, an experimental validation of two types of thrust wire is conducted. Then, the reason why the force errors occurs is discussed.