[Problem] To rationalize production steps for a medical stapler.[Solution] An anvil (A): that forms a medical staple (3) supported in conjunction with a ram (5) in a medical stapler; sutures biological tissue; has dimensions corresponding to the formed peak section in the staple (3) after forming; and has a support section (11) that supports the crown (3b) of the staple (3), and a chamfered corner section (12) formed along both end sections in a direction along the crown (3b) of the staple (3) in the support section (11), which comes in contact with the crown (3b) when the supported staple (3) is formed and regulates a curved section thereof. The chamfered corner section (12) is cured by plastic working and formed.