To efficiently perform stack mount on each substrate block while preventing occurrence of defective components in performing stack mount of upper stage components on faultily mounted lower stage components when performing stack mount of components on each substrate block of a multi-piece substrate.

After mounting lower stage components 24 for stack on each substrate block 22 of a multi-piece substrate 21, the lower stage components 24 are photographed by a camera for mark photographing and mounting conditions of the lower stage components 24 are judged based on the image processing results. Resultantly, when faulty mounting of the lower stage components 24 of any substrate block 22 is detected, stack mount of the upper stage components on the faulty mounting of the lower stage components 24 of the relevant substrate block 22 is skipped and mounting of the other components is allowed. Alternatively, when faulty mounting of the lower stage components 24 of any substrate block 22 is detected, mounting of all components including the upper stage components may be skipped afterwards regarding the relevant block 22.