A semiconductor manufacturing apparatus according to an embodiment includes: a stage to have a plurality of pins to hold a semiconductor substrate having a first surface on which a film to be etched is formed and a second surface positioned on an opposite side to the first surface; a nozzle to eject a liquid chemical toward the first surface of the semiconductor substrate from above the stage; and an optical measurer to radiate light toward the second surface of the semiconductor substrate from a side of the stage during ejection of the liquid chemical, and to measure a displacement amount of the semiconductor substrate based on a state of reception of light reflected on the second surface.