在反托拉斯法(anti-trust laws)或公平交易法(fair trade laws)中，均明文禁止廠商採取價格歧視政策。為研究這項禁令是否恰當，本篇論文建立一個水平差異模型，存在二個不同性質的隔絕市場，一個市場的消費者視所有商品為同質產品，另一個市場的消費者視所有商品為異質產品。在非空間與空間模型的設定下，分別探討在雙佔Bertrand價格競爭下，統一訂價的均衡價格大於差別訂價的兩個均衡價格的條件。我們發現在非空間與空間模型下，均存在某些特定條件使統一訂價的均衡價格大於差別訂價的兩個均衡價格。因此，在這些特定條件下，禁止廠商採取價格歧視政策反而會使得消費者面對較高的價格，這對消費者是不利的。 It is prohibitive for firms to take price discrimination under anti-trust laws or fair trade laws. In order to study the suitability of this prohibition, this thesis constructs a horizontal product differentiation model in which there are two distinct markets: consumers in one market care the difference of products, while consumers in the other do not. We use this model to examine under which conditions that the uniform delivered prices would be higher than the discriminatory prices with spatial and non-spatial models considered, respectively. We show that under certain conditions, the uniform delivered prices could be higher than the discriminatory prices in spatial and non-spatial models. Thus, the probation under anti-trust and fair trade laws would lead to higher prices faced by consumers in these circumstances, which is detrimental to consumers.