A refill includes a peripheral wall defining a space capable of accommodating staples therein. The peripheral wall includes a bottom wall having a first side, a second side opposite to the first side, and a third side connecting end portions of the first side and the second side, a first side wall standing from the first side, a second side wall standing from the second side and opposing the first side wall, and a front wall positioned above the third side and connecting the first side wall and the second side wall. A first opening is formed on the first side wall and the front wall to extend across a boundary between the first side wall and the front wall.