A bump formation method and a bump forming apparatus for a semiconductor wafer are provided in which productivity when bumps are formed onto the semiconductor wafer is improved as compared with the conventional art. The phase values in the partial region are determined with the assumption that the spatial curve of the background phase is a harmonic or quasi-harmonic function, the phase values of the pixels in the partial region being determined based on the phase values in the planar contour. A second test data is obtained by performing a logical NOR operation on the test bits corresponding to the selected test items.