A method of adjusting the brightness of an illuminator in a processing apparatus includes, by a first processing apparatus, storing a sample image obtained by photographing a workpiece with a brightness specified by a first control value, together with the first control value, copying the sample image, the first control value and a processing condition to a second processing apparatus, by the second processing apparatus, storing a plurality of comparative images obtained by photographing the workpiece with brightnesses specified by a plurality of different control values, identifying a control value at a time of photographing a comparative image having a minimum difference in brightness from the sample image as a second control value, by comparing the sample image with the plurality of comparative images, and setting a difference between the first and second control values as a correction value of the control value of the second processing apparatus.