「出於（雙方）不法原因給付，不得請求返還」。如向公務員行賄，使其從事職務上行為，應認給付者亦具有不法原因。此類案例，單就給付者依民法上不當得利，不得請求返還而言，固無疑義；但問題是：為何同樣出於不法原因而受領賄款之人，依法卻能保有不法利益？給付者固然咎由自取，但受領人更值得法律保護嗎？本文從此問題意識出發，指出「透過不法行為之利得，必須被排除」乃整體法規範秩序的共同立場，民、刑、公法皆然。民法不當得利制度只處理到給付人不得請求返還，但受領人能否終局保有該利益，仍應併看民法以外之其他法律，尤其是刑法的利得沒收制度，性質上即是刑法上之（準）不當得利，本文以不法原因給付為核心，探討民、刑法之不當得利制度之交錯問題。 A performance should not be claimed for return if its purpose is unlawful—for instance, the bribery offered to public officials in the an attempt to fulfill their official duties. Consequently, the person who renders performance is considered to be guilty of a breach of law. While the restitution of performance in these cases is not allowed according to the Civil Code of Unjust Enrichment, a question remains: can the recipient of the bribery keep the proceeds legitimately even if his/her purpose is likewise unlawful? Is the recipient actually more worthy of protection? As far as this article is concerned, “the offenders should be deprived of the criminal proceeds” is a general value of the legal system which applies to civil law, criminal law, and administrative law. Therefore, what’s only been dealt is that the person who renders performance for unlawful cause can’t claim the restitution based on the Civil Code. Whether the recipient can keep the proceeds in the end should also consider other regulations or laws besides the Civil Code— especially the Criminal Code of Criminal Proceeds Confiscation, which is essentially the (Quasi-) Unjust Enrichment in the Criminal Code. This article centers on the performance out of a breach of law and deal with the issue of Unjust Enrichment in both the Civil Code and the Criminal Code.