Piezoelectric shunt damping is a technique for vibration suppression by connecting an external circuit called the shunt circuit to a piezoelectric element attached to a mechanical structure. Many previous studies only have considered a single mode for designing shunt circuits. However, the vibration structures typically include multiple vibration modes. This paper inspects the gap between the design for the single-mode system and implementation for the multimode systems. The LR-circuit, which consists of an inductance and a resistor, and the NC-circuit, which consists of a negative capacitor, a resistor, and a negative resistor, are tested. Then, we have found that the spillover phenomenon occurs on the lower frequency side in the multimode piezoelectric NC-shunt damping.