Transthoracic admittance cardiography is a simple and non-invasive method for monitoring cardiac kinetic function. However, its application is relatively limited because few portable devices are available. We have therefore developed a new portable transthoracic admittance cardiograph and its experimental validation of performance has been made in this study. We measured cardiac kinetic function, including heart rate, pre-ejection period, left ventricular ejection period, stroke volume, and cardiac output, in 10 healthy adult male subjects at rest and during exercise using a conventional desktop device as a reference and a newly developed portable device. As a result, high correlations between the desktop and the portable devices were observed in all indices (all <i>r</i>s > .83, all <i>p</i>s < .001). In addition, despite a simple case study, 24-hour continuous ambulatory measurement in a normal daily life using this portable device was confirmed. These results clearly demonstrate the validity of performance and the practicability of this device.