To provide a stapler in which a staple leg of a nonmetal staple can be reliably bent with a small number of components and a simple configuration so as to reduce a cost. A stapler includes a penetration mechanism and a bending mechanism. Hole parts are provided in a pair of cutting blades of the penetration mechanism. The bending mechanism includes first and second bending members which protrude from the hole parts toward between the pair of cutting blades to bend a pair of staple legs, guide surfaces which guide the first and second bending members, and a slide member which drives the first and second bending members. The first and second bending members are provided between the guide surfaces and the slide member.