This paper deals with the constructions and their characteristics of the linear actuators, which a new functional fluid so-called ECF is applied to. ECF is an electric fluid having dibutyl decanedioate as its main ingredient, and a strong flow is generated from the anode to cathode when an electric field is applied to ECF. Tow types of the linear actuators are developed and their characteristics such as driving speed to applied voltage and driving force to driving speed are evaluated.