All‐solid‐state batteries (ASSBs) using non‐flammable inorganic solid electrolyte are expected as a safety energy storage system that exhibits a high energy density. Since external pressure is required to maintain stable interface between active materials and solid electrolyte, the pressure applicable system make the cell modules larger and heavier, and it prevents the practical realization. In the present study, an ASSB system reduced external pressure was achieved by using single‐walled carbon nanotube (SWCNT) assistance. The ASSB electrode mixed with SWCNTs showed high capacity and stable cycle performance even under a coin‐type cell without additional external pressure which is conventionally used on an organic liquid electrolyte system. The unique characters of SWCNT which is high electrical conductivity and self‐supporting force are effective to reduce external pressure of ASSBs. This result opens a new route to design a downsized battery cell.