In a component mounting apparatus, when one of first and second board transfer devices is performing the unloading and loading of boards, a controller operates a component placing device to mount components on a first or second board loaded by the other board transfer device. Thus, it is possible to effectively utilize the time which is taken for the unloading and the loading of either boards, for component mountings on the other board, so that the efficiency in producing boards can be enhanced. Further, since the controller executes a control so that while component mountings are performed on the first boards of M-sheets on the first board transfer device, component mountings are performed on the second boards of N-sheets on the second board transfer device, it is realized to suppress the occurrence of an intermediate stock of either boards where the first boards of the M-sheets and the second boards of the N-sheets are required.