Abstract: In the present invention, a cylinder chamber is provided in a main injector body having a nozzle that injects fuel. In the cylinder chamber, a command piston for driving a needle that opens and closes the nozzle is reciprocably received. A cleaning liquid supply pathway for supplying cleaning liquid and a cleaning liquid discharge pathway for discharging cleaning liquid are connected to the cylinder chamber. As a result, adhesive accretions in the cylinder chamber of the main injector body are discharged out of the cylinder chamber together with the cleaning liquid, and therefore it is possible to prevent a negative effect resulting from the adhesive accretions without using an additive or the like.