In one embodiment, a semiconductor manufacturing apparatus includes a stage on which a substrate is to be installed. The apparatus further includes a light source configured to generate light. The apparatus further includes a shaper including a rotating portion provided with an opening configured to shape the light from the light source, the shaper being configured to irradiate a photomask with the light which has passed through the opening. The apparatus further includes a controller configured to change a width of the light passing through the opening by rotating the rotating portion while scanning the substrate by the light which has passed through the photomask.