Inclusion complex formation between polyaniline with emeraldine base and beta-cyclodextrin has been studied by the frequency-domain electric birefringence (FEB) spectroscopy in a solution of N-methyl-2-pyrrolidone (NMP) and by scanning tunneling microscopy (STM). The FEB results show that polyaniline in the solution with cyclodextrin changes its conformation from coil to rod at low temperature (below 275 K), and some rodlike images are observed on a substrate by STM. These results suggest that cyclodextrins are threaded onto polyaniline and confine the conformation of the polymer chain to a rodlike one. Furthermore, it is found that the threaded cyclodextrins prevent the chemical oxidation, i.e., doping of polyaniline by iodine. This indicates formation of a new inclusion complex, a conjugated conducting polymer covered by insulated cyclic molecules, namely, "insulated molecular wire".