Regioregular poly(3-hexylthiophene) (P3HT) is one of the most widely used polymer semiconductors for electronic applications such as organic solar cells, because of an excellent charge transport property of the film. Recent morphological studies have shown that P3HT films consist of crystalline and disordered phases and that their composition depends on the film processing. However, little is known about the relation between the semicrystalline morphology and macroscopic charge transport properties of the P3HT films. Therefore, it is essential to observe the charge transport properties at nanometer scale and clear the relation between the nanoscale and macroscopic charge transport properties for improving the charge transport of the film. In this study, nanoscale charge transport property in P3HT film was visualized with the resolution of 20 nm by conductive atomic force microscopy (C-AFM). In addition, the relation between the nanoscale conductivity and film morphology was discussed. P3HT films were prepared by spin-coating from chloroform solution onto PEDOT:PSS-coated ITO substrates and then they were thermally annealed at temperatures from 100 to 180 ºC for 10 min. The crystallinity of these films was estimated from the absorption spectra of the films: it increased from 40.5% (for unannealed film) to 45.8% (180 ºC -annealed film). C-AFM current images were measured for these P3HT films with a Au-coated silicon probe at an applied voltage of 1 V on the sample. The current images visualized the growth in the conductivity of the P3HT film. Moreover these images showed that highly conductive domains with the size of approximately 100 nm were formed in the film, and the current flow was not uniform at nanometer scale. The sizes of the highly conductive domains are larger than those of P3HT crystallites previously reported as ~ 20nm, indicating that the highly conductive domains consist of the aggregate of P3HT nanocrystallites. The current flow through the highly conductive nanodomains was increased by thermal annealing, while their domain size remained the same. In addition, the current flow through the highly conductive domains increased by a factor of 2.3 with annealing, whereas the current through the other regions in the film increased by a factor of 1.5. Consequently, thermal annealing increases the inhomogeneous nature of nanoscale hole transport property of P3HT film. This results indicates that the development higly conductive domains are essential for the increase in macroscopic film conductivity.