Substrate polishing method and device

A substrate polishing method includes starting to rotate a circular substrate and polishing an inner peripheral edge surface of a center circular hole formed in the circular substrate into a chamfered or rounded surface by pressing the inner peripheral edge surface against a bypass polishing part of a polishing tape that is conveyed intermittently or continuously and by oscillating the bypass polishing part of the polishing tape about a direction perpendicular to a direction that the center circular hole penetrates through the circular substrate. The polishing tape is guided so as to have an advancing portion advancing toward the circular substrate, a returning portion returning from the circular substrate, and a turning-back portion between the advancing portion and the returning portion guided along a side bypass. The bypass polishing part of the polishing tape is the turning-back portion of the polishing tape.