An electro-conjugate fluid (ECF) is a kind of functional fluid, which produces a jet flow (ECF jet) when subjected to high DC voltage. It is known that a strong ECF jet is generated under nonuniform electric field, for example, the field with a pair of needle and ring electrodes. We developed in our previous study a novel five-fingered flexible robot hand using the ECF. In this study, in order to improve the ECF hand we pay our attention to the flexion of palm because human hand can grasp an object with the flexion of palm. First, we propose a concept of five fingered robot hand which has balloon actuators driven by ECF jet to produce the flexion of palm. The actuator is mainly composed of silicone rubber membrane and a rubber base with a slit, so that when the actuator is pressurized the slit is opened, resulting in making the palm of the robot hand actuate. When the actuator is pressurized with 20 kPa the rubber slit is opened with approximately 60 deg. Finally we investigate the characteristics of the actuator and introduce it into the ECF robot hand.