Biosensing and ion sensing based on graphene field-effect transistor have been investigated. Graphene, a perfect two-dimensional and the thinnest crystal, has high carrier mobility and mechanical strength, and chemically stableness. Therefore, graphene is one of the most suitable sensor materials in solution. However, conventional graphene film has been synthesized by a chemical vapor deposition, which is typically polycrystalline, and needs to transfer to an insulative substrate from the metal catalyst foil. During the transfer process, polymer residues remain on the graphene surface. However, a graphene film on SiC substrates is single crystal with large area, hence, the inherent sensing characteristics are expected in using the epitaxial graphene film on the SiC substrate. Now, we fabricate the functionalized epitaxial graphene field-effect transistors to realize the practical sensing devices.