A component mounting machine comprising: a moving device configured to move between a component supply position and a circuit board; a mounting head provided on the moving device and configured to pick up a component supplied to the component supply position and mount the picked-up component on the circuit board; a component camera configured to image the component held by the mounting head from below the mounting head; a board camera provided on the moving device and configured to image the circuit board from above; an imaging position memory section configured to memorize imaging position coordinates that are position coordinates of the moving device during imaging by the component camera, based on image data acquired by imaging of the mounting head by the component camera; a relative position memory section configured to memorize relative position coordinates that are a relative position of the mounting head with respect to the board camera; a correction necessity determining section configured to perform imaging of the mounting head by the component camera when the moving device has arrived at the imaging position coordinates, and determine whether it is necessary to correct the relative position coordinates memorized in the relative position memory section, based on a position of the mounting head understood from image data acquired from the imaging by the component camera; and a measuring section configured to measure a positional deviation amount between an actual position of the mounting head, which is the position of the mounting head understood from the image data acquired from the imaging by the component camera, and a position of the mounting head calculated based on the imaging position coordinates, wherein the correction necessity determining section is configured to determine whether it is necessary to correct the relative position coordinates memorized in the relative position memory section based on the positional deviation amount measured by the measuring section. a moving device configured to move between a component supply position and a circuit board; a mounting head provided on the moving device and configured to pick up a component supplied to the component supply position and mount the picked-up component on the circuit board; a component camera configured to image the component held by the mounting head from below the mounting head; a board camera provided on the moving device and configured to image the circuit board from above; an imaging position memory section configured to memorize imaging position coordinates that are position coordinates of the moving device during imaging by the component camera, based on image data acquired by imaging of the mounting head by the component camera; a relative position memory section configured to memorize relative position coordinates that are a relative position of the mounting head with respect to the board camera; a correction necessity determining section configured to perform imaging of the mounting head by the component camera when the moving device has arrived at the imaging position coordinates, and determine whether it is necessary to correct the relative position coordinates memorized in the relative position memory section, based on a position of the mounting head understood from image data acquired from the imaging by the component camera; and a measuring section configured to measure a positional deviation amount between an actual position of the mounting head, which is the position of the mounting head understood from the image data acquired from the imaging by the component camera, and a position of the mounting head calculated based on the imaging position coordinates, wherein the correction necessity determining section is configured to determine whether it is necessary to correct the relative position coordinates memorized in the relative position memory section based on the positional deviation amount measured by the measuring section.