A transient pulse methos has been used to measure the permeability of Pocheon granite pre-heated from $25^{circ}C$ to $600^{circ}C$ at effective pressure up to 32MPa. The permeability of whole rock ranged from 0.72 $mu$d at 10MPa to 0.20 $mu$d at 32MPa. The permeability of rock heated to $600^{circ}C$ ranged from 18.07$mu$d at 10MPa to 6.39$mu$d at 32MPa. Confining pressure has greater effects on the rocks thermally treated to lower thermal-cycle temperatures than on the higher thermally treated rocks. The increase of permeability is most pronounced between 40$0^{circ}C$ and $600^{circ}C$. Below 40$0^{circ}C$, permeability increase is expected to be associated with the formation of new cracks and widening of preexisting cracks, whereas above 40$0^{circ}C$, permeability increase is expected to reflect widening of cracks. Using the equivalent channel model, author shows that the exponent n in the relationship relating the permebility(k) to porosity($phi$) by k∝$$phi$^n$</TEX> falls in the range 2.7$leq$n$leq$3.0.