關稅化是世界貿易組織（WTO）長期以來所提倡的政策，其目的在將非關稅貿易障礙轉換為關稅貿易障礙。本文以一個兩國模型探討進口國政府對平行輸入商品實施關稅化政策所產生之福利效果並進一步討論關稅化政策對於進口國製造商研發投入的影響。本文發現，無論製造商採取一部訂價或兩部訂價，關稅化政策都將使進口國福利下降。但關稅化對製造商研發投入的影響卻會因其訂價模式而有所不同。若製造商採兩部（一部）訂價法，關稅化政策將減少（不影響）其研發投入。此一結果顯示，若一國之製造商採兩部訂價法，且其政府對於平行輸入商品實施關稅化政策，長期而言將會導致該國福利惡化。

WTO has long called for converting non-tariff barriers into tariffs. This is called tariffication. Utilizing a two-country model, this paper examines the welfare effect of tariffication on parallel trade. We also compare the R&D levels of the manufacturer before and after tariffication. It is found that tariffication is socially undesirable for the domestic country no matter whether the manufacturer adopts one-part or two-part tariff pricing. But the effects of pricing on the manufacturer's R&D are very different. If the domestic manufacturer adopts two-part (one-part) tariff pricing, tariffication discourages (has no effect on) the R&D investment of the domestic manufacturer. This implies that domestic welfare worsens in the long run under two-part tariff pricing.