Interfacial resistance is one of the severe problems in composite electrodes of all solid state batteries (ASSBS), especially oxide type ASSBs. Conflicts between poor sintetability and possible unfavorable reaction with active materials limit applicable materials and processes hi this report, a novel approach is proposed to decrease grain boundary resistance among nonsintered solid electrolyte particles. The concept is successfully demonstrated, and the nonsintered grain boundary resistance of a highly conducting solid electrolyte (Li1.3Al0.3Ti1.7(PO4)(3)) was suppressed by being coated with poorly conducting solid electrolyte (Li2SiO3). Increased total conductivity and variation of apparent activation energy are well explained from the viewpoint of defect cliernistry.