A unit exchanging device for automatically exchanging a component supply unit between multiple component mounting devices in which multiple component supply units for supplying components are detachably installed includes: a gripping portion for gripping the component supply unit; a moving section for moving the gripping portion along a predetermined direction between a position for attaching/detaching the component supply unit to and from a component mounting machine; and a control section for controlling the gripping and release of the gripping of the component supply unit by the gripping portion and controlling the moving section so as to change the standby position in accordance with the gripping state of the component supply unit in the gripping portion.