Transverse tensile fracture surfaces of carbon fiber unidirectionally reinforced epoxy composites (CFRP) were examined by a scanning electron microscopy, in order to understand micromechanics of the failure at the interface. The tensile tests were carried out in two directions. One was transverse in prepreg sheets plane (Y direction), and the other was perpendicular to the prepreg sheets plane (Z direction). It was observed that many parts of the fiber/matrix interface were fractured in the fracture surfaces of the CFRP using unsurface treated carbon fiber. But in contrast, in the fracture surfaces of the CFRP using surface treated carbonized fiber, the failure was largely occured in the matrix. The effect of sizing of the fiber on the fractography could not be detected. In the transverse tensile fracture surface of Y direction, the row of 'cusps' at resin fracture surface near broken fiber was observed. On the other hand, the fracture surface of Z direction was more flattish than that of Y direction. And areas of 'river' and 'scarp' parts in the fracture surface of Z direction were larger than that of Y direction. The transverse tensile strength of Y direction was 30-40% higher than that of Z direction. These differences in Y and Z directions are considered to be due mainly to the anisotropy of fiber misorientation angle and the difference of the surface condition of the specimens.