Soft robots inspired from natural systems are one of the main research topics in the robotic field since the last decade. Accordingly, artificial muscles were widely investigated due to their potentials in soft machines or soft robots. Many types of artificial muscles have been developed, including pneumatic actuators, ion-exchange polymer composite actuators, polymer gels, shape memory alloys, and so on. However, these artificial muscles are not used as practical actuators. In this study, the authors propose a new type of micro artificial muscle actuator (< 1 cm3) utilizing an electro-conjugate fluid (ECF) which generates a powerful jet flow when subjected to a high voltage (∼ kV). The actuator basically consists of a fiber-reinforced silicone rubber tube and a micro pressure source using the ECF. The inner pressure of the silicone rubber tube is increased by the jet flow generated at the pressure source. The silicone rubber tube contracts along the actuator axis with the increasing pressure. The driving characteristics of the micro artificial muscle actuator were experimentally investigated. The experimental results show that this new actuation technology' yields great potentials for driving soft robots.