A piezoelectric substrate manufacturing device that includes first and electrodes that face each other with a piezoelectric substrate interposed therebetween; a cover that surrounds the second electrode such that the leading end of the second electrode is exposed; a supply unit that supplies a processing gas to an internal space of the cover; a processing unit that performs surface processing on the piezoelectric substrate by applying a voltage between the first and second electrodes causing the processing gas to change into plasma; a detector that is provided outside the cover with its relative position fixed with respect to the second electrode; a measurement unit that measures the thickness of the piezoelectric substrate using the detector; a driving unit that changes the relative positions of the first and second electrodes; and a control unit that controls the supply unit, the processing unit, the measurement unit, and the driving unit.