We investigated the local ferroelectric polarization switching characteristics of an epitaxial (001) BiFeO3 (BFO) thin film and BFO nanodots having 100-300-nm diameters. The 30-nm-thick BFO thin films were deposited on (100) Nb-doped SrTiO3 (Nb:STO) substrates via pulsed laser deposition. This large switching voltage of the BFO thin film originates from the neighboring domains that stabilize the ferroelectric polarization nanobit against the switching electric field induced by the external bias. The coercive voltages of the piezoelectric d(33) hysteresis loops, which depend on the diameters of the BFO nanodots, were saturated to that of the BFO thin film, indicating that the influence of the neighboring domains is limited to within a diameter of approximately 300 nm.