Short-distance (propagation distance less than 1,000 km) VLF subionospheric propagation is, for the first time, used to study the solar flare induced D-region perturbations of the lower ionosphere. We have used two years data for a propagation path from the Japanese VLF transmitter (call sign JJI, frequency = 22.2 kHz, and located at Ebino, Kyushu) to a receiving station of Chofu, Tokyo. For the sake of comparison, we have also used the long distance VLF path (NWC-Chofu). First of all, the value of perturbation in amplitude (ΔA) for the short-distance path seems to be much more enhanced (ΔA = 8~9 dB) for this short-path than the long-distance paths previously studied. The experimental value of ΔA is found to monotonically increase with the logarithm of X-ray flux. This dependence is numerically simulated by means of the FDTD (finite difference time domain) method to deduce the D-region perturbation, {1 + C exp {-(z - z 0)2/2¿ 2} (C: enhancement factor, z0: reference height and ¿: vertical extent) (this modification seems to be much more realistic than the previous two parameter modeling in an exponential profile). The numerical computations with z0 ~60 km and ¿ ~ 10 km have shown that the value of ΔA increase up to ~6 dB in a range of X-ray flux from C = 10 to C = 103. As the conclusion, the ΔA is closely related with the logarithm of solar X-ray flux, so that we will be able to deduce the C value from the observed ΔA value.