Component mounting method using a component mounting device that is configured to hold a plurality of suction nozzles, which are configured to suck a component, so as to be replaceable at a predetermined gap on a rotary head in the circumferential direction thereof, the component mounting device comprising: an imaging device which is configured to collectively capture a side surface image of at least a portion of the suction nozzle which is raised in order to carry out a component suction and mounting operation or a nozzle replacement operation out of the plurality of suction nozzles that are held by the rotary head, and a side surface image of at least the lower end section of the two suction nozzles (13A, 13C) which are positioned at both sides of the suction nozzle; and an image processing device which is configured to process the image which is captured by the imaging device, wherein the imaging device has one image sensor and an optical system unit that is configured to form a side surface image of an imaging target part of each of the three suction nozzles (13A, 13B, 13C) on a light-receiving surface of the image sensor such that the side surface images do not overlap, the component mounting method being characterized by causing the image processing device to process images of the two suction nozzles (13A, 13C), which are positioned on both ends of the row of the three suction nozzles (13A, 13B, 13C), that are captured as imaging targets during the component suction and mounting operation so as to confirm whether or not the suction nozzles (13A, 13C) suck a component and the suction posture of the components, and to process the image of the suction nozzle, which is positioned at the middle of the three suction nozzles (13A, 13B, 13C) that is captured during nozzle replacement operation, as the imaging target to recognize the presence or absence of the suction nozzle. an imaging device which is configured to collectively capture a side surface image of at least a portion of the suction nozzle which is raised in order to carry out a component suction and mounting operation or a nozzle replacement operation out of the plurality of suction nozzles that are held by the rotary head, and a side surface image of at least the lower end section of the two suction nozzles (13A, 13C) which are positioned at both sides of the suction nozzle; and an image processing device which is configured to process the image which is captured by the imaging device, wherein the imaging device has one image sensor and an optical system unit that is configured to form a side surface image of an imaging target part of each of the three suction nozzles (13A, 13B, 13C) on a light-receiving surface of the image sensor such that the side surface images do not overlap, the component mounting method being characterized by causing the image processing device to process images of the two suction nozzles (13A, 13C), which are positioned on both ends of the row of the three suction nozzles (13A, 13B, 13C), that are captured as imaging targets during the component suction and mounting operation so as to confirm whether or not the suction nozzles (13A, 13C) suck a component and the suction posture of the components, and to process the image of the suction nozzle, which is positioned at the middle of the three suction nozzles (13A, 13B, 13C) that is captured during nozzle replacement operation, as the imaging target to recognize the presence or absence of the suction nozzle.