[Problem] To provide a cleaning system, a cleaning unit, and a cleaning method that provide enhanced cleaning performance. [Solution] The present invention is provided with: a tubular reservoir which holds a pH adjusting liquid therein and which has a hollow space above the pH adjusting liquid； a filling passage which is connected to the top of the reservoir and through which carbon dioxide gas is filled in the hollow space at a constant regulated pressure； a carbon dioxide gas cylinder which is connected to an input side of the filling passage； a liquid delivery passage which is connected to a lower part of the reservoir and through which the pH adjusting liquid is delivered to a conduit of a to-be-cleaned instrument at a regulated pressure； a liquid concentrate introduction passage which is connected to the reservoir and through which a cleaning liquid concentrate used to prepare the pH adjusting liquid is introduced into the reservoir； and a liquid concentrate tank which is provided to an input side of the liquid concentrate introduction passage so as to store the cleaning liquid concentrate therein. The regulated pressure is obtained after regulating the filling pressure of the carbon dioxide gas cylinder by a filling pressure regulator provided to the filling passage and a liquid delivery pressure regulator provided to the liquid delivery passage. The conduit of the to-be-cleaned instrument is cleaned with the pH adjusting liquid.Le problème décrit par la présente invention est de fournir un système de nettoyage, une unité de nettoyage et un procédé de nettoyage qui fournissent des performances de nettoyage améliorées. A cet effet, la présente invention comprend : un réservoir tubulaire qui contient un liquide de réglage de pH à l'intérieur de celui-ci et qui a un espace creux au-dessus du liquide de réglage de pH ； un passage de remplissage qui est relié à la partie supérieure du réservoir et à travers lequel du dioxyde de carbone gazeux est introduit dans l'e
