PURPOSE: To provide a sealing device for a bolt where the structure of sealing is hard to become clear and the discharge of sealing is difficult, and also reuse is possible at the time of sealing.

CONSTITUTION: A bolt 11 is screwed in a pump housing 14, and this bolt 11 is tightened to the pump housing 14 with a fastening nut 15. A sealing member 16 covers the periphery of the fastening nut 15. A pin 17 is press-fit in a shaft 13, being driven into an insertion hole 13b from one insertion hole 16b. The axial length of the pin 17 is set to be shorter than the inside diameter of the second engaging part 16c and besides to be longer than the inside diameter of an internal thread part 16b, so the sealing member 16 becomes impossible to be taken out of the bolt 11 by being locked to the pin 17. It is very difficult for a user who does not know the structure of a sealing device to cancel this sealing condition.