Carbon-fiber-reinforced plastic (CFRP) is a structural material with excellent mechanical properties. However, CFRP is a brittle material, so defects must be detected early. Moreover, it is important to precisely detect any misalignments of carbon fibers in the CFRP to maintain its reliable mechanical properties. In this study, we used eddy current testing with a mutual induction-differential probe to detect various orientations of carbon fibers in CFRP specimens. We could identify the fiber orientations in three types of CFRPs—unidirectional, cross, and quasi-isotropic orientations—with stable signals.