Wearable devices have rapidly developed in recent years. The practical applications of wearable devices utilize secondary batteries such as lithium-ion batteries. Biofuel cells are a promising next-generation power source for these devices because they can be operated under mild conditions. Nanocarbons are essential materials owing to their excellent electrical conductivity and high surface area. However, nanocarbons easily aggregate, which results in an electrochemical active surface area significantly smaller than their theoretical individual surface area. Although carbon nanotubes (CNTs) have high electrical conductivity owing to their network structure and large specific surface area, it is well known that CNTs form bundled structures by aggregation. In this study, to completely exploit the properties of CNTs, a modified electrode was fabricated using a nanocarbon composite material with CNTs as the base material. Laccase bio-electrocatalysis tests were conducted, and the results clearly demonstrated the composite effect of CNTs with different nanocarbon morphologies, such as Ketjen black.