A hood attachment jig includes a holding member whose diameter is increasable and that holds an endoscope hood in a state where the holding member is inserted into the endoscope hood a diameter increasing member that increases the diameter of the holding member by entering the holding member, so that the diameter of the endoscope hood increases and a push-out member that, when an attachment operation is performed in a state where a tip portion of the endoscope enters the holding member with the increased diameter, pushes out the holding member and the endoscope to separate the holding member and the endoscope from the diameter increasing member so that the endoscope hood, a force of restitution of which reduces the diameter of the holding member, is brought into contact with an outer circumferential surface of the tip portion of the endoscope and further pushes out the endoscope to detach the endoscope from the holding member so that the endoscope hood is attached to the endoscope tip portion.
