An enclosure member includes a throughhole that penetrates a cover portion. The cover portion includes a blocking portion that receives an abutment by a wall portion to close an opening of an outflow passage with respect to spaces outside of the enclosure member. The blocking portion is provided so as to surround an opening of the throughhole, and the throughhole is in communication with the outflow passage even when the blocking portion is abutting the wall portion. Further, a spring is outside of a back pressure chamber to bias the enclosure member. The enclosure member itself blocks outside spaces from the back pressure chamber, so the expenditure of high pressure fuel may be controlled, and an injection hole may be opened and closed by a needle.