A medical bag of multi-liquid missing type for one-shot operation for opening the weak seal portion, which makes it possible to obtain simultaneous opening of a blending medicine inlet.The medical bag 10 is formed of a soft film material and having a weak seal portion, which divides the space inside the bag into a plurality of compartments 20 and 22. A blending medicine inlet port 14 is arranged adjacent the one compartment 20. The inlet port 14 includes sealed compartments 36A, 36B and 36C for storage of the respective blending medicines. The inlet port 14 is usually closed by a peel film member 44 for preventing the blending medicines from being discharged. The peel film member 44 is strongly adhered to the opposed surface of the plastic film constructing the medical bag. An integral movement of the peelable member with respect to a widening displacement of the medial bag is obtained when the weak seal 18 is opened under a pressing force, so that the peelable member 44 is separated from the inlet port 14, resulting in a discharge of the blending medicines from the compartments 36A, 36B and 36C into the medical bag.
