After one suction nozzle turns from one arrangement pitch ahead of a work position toward the work position and immediately before the suction nozzle starts descent at the work position, an image of a side portion of the suction nozzle is captured. Parameters are used for controlling the imaging operation. The parameters include descent start timing when each of the suction nozzles starts descent during mounting of an electronic component, and data required for determining an imaging time necessary from when a camera starts imaging of the suction nozzle until the camera ends the imaging. Imaging is completed immediately before the one suction nozzle starts descent at the work position.