Abstract: A locking device for a valve having a rotatable stem extending from a body and a handle secured to the stem for the purpose of preventing rotation of the handle and movement of the valve member. A fixed locking member is mountable on the valve body. A movable locking member is mounted on the handle for rotation therewith and for relative movement outwardly and inwardly of the valve body and fixed locking member. Interfitting cooperating members on the fixed locking member and the movable locking member are engaged at a desired position of the valve member upon inward movement of the movable locking member relative to the fixed locking member to prevent rotation of the handle and are disengaged to permit rotation of the handle upon outward movement of the movable locking member relative to the fixed locking member.