A multi-layer piezoelectric element includes: a stacked body in which piezoelectric layers and internal electrode layers are laminated; a conductor layer disposed on a side face of the stacked body; a conductive joining material layer disposed on a surface of the conductor layer; and an external electrode joined to the conductor layer via the conductive joining material layer, the conductive joining material layer comprising solder and a conductive adhesive, the solder constituting an end of the conductive joining material layer which end confronts an end of the external electrode to be connected to an external circuit. There is provided a multi-layer piezoelectric element which suppresses separation of an end on an input/output side of the external electrode and is driven stably for a long period of time, an injection device and a fuel injection system which are provided with the multi-layer piezoelectric element.