To provide a fastener capable of positively attaching an electric appliance to a utility pole.

The fastener is provided with a bolt member having a columnar part, a male screw part with an axis formed on one end of the columnar part so as to match with an axis of the columnar part, and a collar part formed on another end of the columnar part, a fastening member having a tabular part 14, a hole part 16 piercing the tabular part 14 in a thickness direction, and slot parts with one opened to a side face 18 of the tabular part 14, and another opened to the hole part 16, and a nut member having a female screw part screwed on the male screw part. An outer diameter of the columnar part is larger than an outer diameter of the male screw part, and it is smaller than an outer diameter of the collar part. A width size W1 of the slot part is a size allowing loose fitting of the male screw part in the slot part, and smaller than the outer diameter of the columnar part. An inner diameter size D of the hole part is a size allowing loose fitting of the columnar part in the hole part, and smaller than the outer diameter of the collar part.