在真實世界中，事業為謀私益，聚集市場力以達成目的，並非罕見；為免上述舉措破壞市場功能，各國競爭法制無不將聯合行為列為管制態樣。又事業為規避管制，無不勉力避免留下其間勾串聯合行為之相關事證，致使合意之證明成為聯合行為管制上相當棘手之問題。對此，比較法上發展出「一致性行為理論」及「合理推定原則」，適度緩解競爭法主管機關之管制難題；另一方面，事業亦相應地立於經濟學觀點提出「價格跟隨行為」以為抗辯。然上述理論及原則是否得逕以適用於我國法上，尚非無疑。本文所探討評析之案例，即係兩造當事人援引上述學理攻防之真實個案，從而吾人得自該案例之法院判決中，觀察我國司法實務對於前述問題之回應。

Concerted action and price follow-up usually occur in the oligopolistic market, the former is prohibited by Taiwan fair trade act, the latter is not. Those two acts are quite similar in appearance, and the crucial point of proving concerted action is the existence of mutual understanding among the enterprises. Because the direct evidences usually acquire great effort to acquire, the use of indirect evidences becomes very important for Fair Trade Commission to facilitate the detection and proving of the mutual understanding. The main purpose of this essay is to discuss and analyze foregoing problems by reviewing the case of concerted pricing of industrial paper products among three leading paper corporations in Taiwan.