An instrument for detection of a shielding effect of RF magnetic fields (2-8 MHz) has been developed to investigate the characteristics of the superconductivity (SC) of some [Pd(dmit)(2)] salts. The main part of the system consists of two LC oscillators, which can operate at low temperatures. The shielding signal due to a superconducting transition of the sample in the coil is detected as an increase of the frequency of the RF output. The coils are set within a clamp-type pressure cell. SC in a few [Pd(dmit)(2)] salts was investigated by using this system. An increase in the frequency was observed below 4 K under pressure. This may indicate the existence of the superconducting transition of the [Pd(dmit)(2)] salts. However, the shielding signal was about 10(-2) times as small as that observed in an ordinary organic superconductor such as kappa-(BEDT-TTF)(2)Cu[N(CN)(2)Br]. This peculiarity of the SC in the [Pd(dmit)(2)] salts is reported.