Electrical resistivity at the magnetic axis &eegr;(R) and at the separatrix &eegr;(rs) of a field‐reversed configuration (FRC) plasma produced by theta pinch machines are estimated from detailed interferometric measurements, assuming that the temperature is uniform within the separatrix. The ratiof0[=&eegr;(R)/&eegr;(rs)] increases with the beta value at the separatrix &bgr;s, which is consistent with the fact thatf0decreases whenxs(separatrix radius normalized by the inner radius of a theta pinch coil) increases [Phys. Fluids28, 888 (1985)]. This tendency is a natural consequence of the transport properties of the FRC plasma when the particle confinement time is nearly equal to the decay time of the trapped reversed magnetic flux, as is normally the case. Theoretical expectations of the anomaly of &eegr;(rs) over the classical resistivity &eegr;0increases and decreases slightly with &bgr;sfor the case of the lower hybrid drift and the low‐frequency drift instability, respectively. On the other hand, the observed &eegr;(rs)/&eegr;0decreases substantially with &bgr;s. [The value of &eegr;(rs)/&eegr;0changes from about 15 to 5 as &bgr;schanges from 0.45 to 0.6.]