When an infusion device is to be fixed and detached to and from the pole of an infusion stand, the time loss and physical load imposed on an attendant are minimized by omitting the operation of repeatedly and continuously rotating a rotating knob while holding the infusion device. A clamp apparatus (20) includes a clamp base (1) on which a grip-shaped portion which grips one outer peripheral surface of the pole of an infusion stand and an upright shaped portion are formed, and a main shaft member (5) having one end rotatably provided with a grip member which grips the other outer peripheral surface of the pole, and the other end to which a rotating knob is fixed, and sets a gripped state or an ungripped state relative to a pole (30) by moving a grip member (8) when a rotating knob (9) is rotated clockwise or counterclockwise. This apparatus includes a tubular thread member (2) which has thread portions formed on its inner peripheral surface and through which a main shaft member extends, a pair of male thread pieces (4) which are built in the housing portion of the main shaft member and set a meshed state and unmeshed state relative to female thread portions, and an operation means (103) including an operation portion (3f) which is placed to be movable between an operation position set when the rotating knob is moved and a separate position set when the rotating knob is not moved, and sets the pair of male thread pieces in the unmeshed state.
