A new system has been developed for obtaining electrographic potential through thin underwear inserted between the measuring electrodes and the skin of a neonate or an infant when lying supine. The system is based on capacitive coupling involving the electrode, the underwear, and the skin. Validation of the system revealed the following: (1) the signal detected using the system displayed a periodic waveform synchronized with the simultaneously recorded ECG, even when thin underwear was inserted between the electrode and the skin, (2) the gain of the system when the cloth was inserted decreased as the frequency increased. The present system appears promising for application to bedding as a non-invasive and awareness-free method for ECG monitoring of neonates or infants. However, there is still room for improvement in terms of its practical use, because the high-frequency component of the signal was depressed in comparison with the reference ECG.