To provide a new means of settlement applicable to injection of an additive medium and accordingly provide a means of settlement to remove a defective point of public technology, applicable to injection of water, constituted simple and compact and high in operational reliability.

An injection valve device is constituted to be furnished with a valve element part 2 having a first chamber 4, the first chamber 4 is communicated to a cylinder combustion chamber through at least one of nozzle holes 5a, 5b, an additive medium is continuously supplied to the first chamber 4 through supply ducts 8, 8a, a slender valve member 6 of an injection valve 3 controls supply of the additive medium to the combustion chamber from the chamber 4, it is pressurized toward a valve closing position by a spring 7, and injection of the additive medium is prevented at the valve closing position.