An object of the present device is to provide a cover capable of preventing the administration of unmixed medicaments to a patient. The cover for being mounted on a multi-compartment infusion bag of the present device is a cover for being mounted on a multi-compartment infusion bag including a plurality of compartments partitioned by at least one easily peelable partitioning seal portion which is opened in response to an increase in the internal pressure of at least one of the plurality of compartments induced by pressing said at least one of the plurality of compartments. The cover has a pair of pinch members that pinch at least one of the plurality compartments. The pair of pinch members has engaging elements that engage each other to maintain a pinching state of the pair of pinch members until the pinching state is released in response to an increase in the internal pressure of said at least one of the compartments so that the suspension portion can be used. The pair of pinch members cover a suspension portion in the pinching state for preventing the use of the suspension portion for suspending the infusion bag until said at least one easily peelable sealing partition is opened.