The present energy treatment device has an insertion part, a pair of arms which are provided in a distal portion of the insertion part and which are capable of performing an opening-closing operation, a treatment member which is attachably and detachably provided in a first arm, a locked part which is provided in a second arm and which is capable of locking the treatment member, and a manipulation part which causes the pair of arms to perform an opening-closing operation, wherein the treatment member includes a knife wire, and a locking member which is positioned with respect to the first arm, being attachable to and detachable from the first arm, and capable of being locked by the locked part, the locked part has a retainer which is capable of holding the locking member with a force stronger than a force of the first arm to hold the locking member.