This proposal describes a muSR experiment on a garnet-type Li ionic conductor, Li6.75La3Zr1.75Nb0.25O12 under electric field (E) in order to study a diffusive behavior under a potential gradient. According to our preliminary experiment in 2012, the applied pulsed E was found to clearly change a relaxation behavior at 350 K and E=10kV/cm and -10kV/cm. However, due to a limited beam-time, we only measured the ZF-spectra under E with a fixed pulse width (40 microseconds). We, therefore, wish to propose a continuation muSR experiment on the garnet-type ionic conducting compounds in order to know the effect of the pulse width, pulse timing, pulse height, temperature, and polarity of E on the diffusive behavior.