To promote recycling of carbon fiber reinforced plastics (CFRPs), we investigated the removal mechanism of resin by electrical treatment at high voltage. Using the pseudo in-situ observations, we found that resin removal was triggered by electrical treatment. Based on the observations and current dependency, the resin was removed by a mechanical approach that employed the oxygen gas generated from water electrolysis, i.e., the gas peeled the resin. Moreover, the cathodic treatment was unable to achieve the resin removal because of the high diffusion of hydrogen gas into the epoxy resin. During anodic treatment, CO, CO2, and oxygen gases were generated from the specimen, and damage to the carbon fiber (CF) was observed on the specimen after treatment for 180 min. The mechanism of the resin removal was governed by the resin peeling off from the CFRP composite, which was triggered by the oxygen gas generated from the water electrolysis. During electrical conduction, the peeling was initiated at the voids that were formed by the oxidation of the locally heated resin spots. At low resin content levels, the CF was subjected to damage due to the electrical conduction, which was accompanied by the application of a high voltage.