Polyethylene composites filled with various types of carbon fiber were prepared for electrical and thermal conductivity measurements. By estimation of the anisotropic parameter (Hermans’ parameter), the fibers were confirmed to be significantly biaxially oriented in the composites. The critical volume fractions in the electrical conductivity of these composites for the two oriented directions (X and Y) were equal to each other and smaller than that for a direction (Z) vertical to the above. The electrical anisotropy, i.e., ratio of electrical conductivity of the composite for the Z direction to the X and Y directions varied drastically with increase in filler content. The longer the length of carbon fiber was, the higher became the electrical conductivity of the biaxially oriented carbon fiber composites for all directions. But, the thermal conductivity of the composite was almost unchanged for the Z direction, even if fiber length was sufficiently long. Our equation, previously proposed, proved adaptable to these thermal conductivities. The factors of C(p) and C(f) in the equation are kept unchanged, in spite of increasing fiber length.