Since the thermal anisotropy of carbon-fiber-reinforced plastic (CFRP) depends on the direction of the carbon fibers, it is important to understand the thermal characteristics of CFRP in a three-dimensional thermal propagation. To reveal the relationship between the direction of the carbon fibers and the preferred thermal orientation, we developed a method of estimating thermal anisotropy by analyzing the dependence of measured phase lags on the distance from a heating spot, on the basis of a periodical heating method. Measurement results of the CFRP samples with different fiber orientations in the thickness direction, fabricated by hot pressing, showed a mismatch between the fiber and thermal orientations. It was found that the fiber orientation is not necessarily in conformity with the thermal orientation. The proposed method might be effective for evaluating the thermal anisotropy of CFRP.