Abstract: An electro-coagulation printer is basically constructed by a rotation drum having a circumferential surface which is electrified in positive potential, a number of electrodes which are selectively electrified in negative potentials, and an ink supply device. The electrodes are aligned to oppositely face with the circumferential surface of the rotation drum with a gap which ranges between thirty and one-hundred microns. The ink supply device is arranged in an incoming side of the rotation drum and supplies liquid ink to be injected onto the circumferential surface of the rotation drum, so that electrification is performed between the electrodes and circumferential surface of the rotation drum with intervention of the liquid ink. Thus, a desired image is formed on the circumferential surface of the rotation drum and is transferred onto a printing material such as a paper.