Disclosed herein are a compact activation member for operating a medical treatment tool, an activation mechanism having the activation member, and a method for fabricating the activation mechanism. An activation member is directed to an activation member which is provided in a housing so as to be rotatable about a rotational axis and around which an elongate element for operating a treatment tool is wound. The activation member includes: a plurality of rotation members which rotate about the rotational axis； and a pressing member which engages with at least one of the plurality of rotation members. Each of the plurality of rotation members includes a surface provided with ridges and grooves. The plurality of rotation members are attached to a base of the housing by being pressed by the pressing member in an extending direction of the rotational axis, with the surfaces of the plurality of rotation members engaged with each other.
