An object detecting method includes dividing a standard pattern into two or more areas radially from a central point; selecting, in each divided area of the standard pattern, a standard pattern pixel position at the maximum distance from the area dividing central point as a standard pattern representative point; dividing a determined pattern into two or more areas; selecting, in each divided area of the determine pattern, a determined pattern pixel position at the maximum distance from the area dividing central point as a determined pattern representative point; determining a positional difference between the standard pattern representative point and the determined pattern representative point in the corresponding divided areas; and determining the determined pattern as a target object when the positional differences in all of the divided areas are within a predetermined range.