The four-probe electrical resistivity measurements on a single-component molecular semiconductor [Ni(ptdt)(2)] (Ni(S8C9H2)(2)) was performed up to 20.7 GPa by using a diamond anvil cell. A newly improved method was employed to reduce the effect of uniaxial pressure. The semiconducting behavior persisted up to 17.9 GPa. The pressure-induced metallization began to appear at 18.9 GPa, and the complete metallic behavior down to 1 K was observed at 19.9 GPa.