A component mounting device includes a mounting head that mounts a component at a mounting position on a substrate, an imaging section capable of imaging the mounting position on the substrate, and a controller that determines a mounting state by comparing images of the mounting position before and after mounting of the component captured by the imaging section. The controller is configured to determine the mounting state by comparing the images before and after mounting of the component during operation from completion of mounting of the component to completion of mounting of a subsequent component.