KEY WRENCH

In the present invention, N is defined as any natural number of 3 or greater. A key wrench is provided with a key portion (5-2) capable of engaging in an N-gonal hole (2), and a proximal-end portion (5-1). The key portion (5-2) is provided with N side faces including a first side face (50-1), a second side face (50-2), and an Nth side face (50-N). The first side face (50-1) is a tapered face, andthe Nth side face (50-N) is a non-tapered face. A key wrench is thereby provided in which deformation of the surface of the hole is suppressed and the occurrence of an excessive come-out load is suppressed. 将N定义为3以上的任意的自然数。内角扳手具有能够与N边形的孔(2)卡合的工作头部分(5-2)和基端部分(5-1)。工作头部分(5-2)具有包含第侧面(50-1)、第二侧面(50-2)及第N侧面(50-N)在内的N个侧面。第侧面(50-1)是锥面，第N侧面(50-N)是非锥面。由此，提供抑制孔表面变形并且抑制产生过大的脱离载荷的内角扳手。