To provide a three-component mixing device with which anybody can mix three medical agents easily and uniformly when preparing a three-component mixed adhesive, for example, for a surgical or dental operation (treatment). The three-component mixing device comprises: a syringe having a medical agent injection hole at a tip end thereof and in which a first gasket and a second gasket are slidably disposed, wherein a first medical agent is contained between the medical agent injection hole and the first gasket and a second medical agent is contained between the first gasket and the second gasket and a plunger having an axial penetration hole, wherein a medical agent container containing a third medical agent is detachably attached to a rear end of the plunger, and a frontal end of the plunger is slidably inserted in the syringe. The plunger is slid in the syringe from the rear side to the front side of the syringe so as to supply the third medical agent from the medical agent container to the inside of the syringe through the penetration hole for sequentially mixing the third medical agent, the second medical agent, and the first medical agent in the syringe and injecting the resulting three-component mixture to the outside through the medical agent injection hole.
