In accordance with an embodiment, a substrate measurement apparatus circuit includes a light source, a detector, a data calculation unit, a mirror unit, a mirror drive unit, and a mirror drive calculation unit. The light source applies the electromagnetic waves to a measurement target substrate. The detector detects the electromagnetic waves diffracted or scattered by the application of the electromagnetic waves to the substrate. The data calculation unit processes a signal from the detector to acquire substrate information. The mirror unit includes a deflecting mirror which is adjusted to an optical condition where incident electromagnetic waves are totally reflected to control the track of the electromagnetic waves. The mirror drive unit drives the deflecting mirror in at least one of vertical, horizontal, and rotational directions. The mirror drive calculation unit calculates a drive amount to drive the deflecting mirror in at least one of the vertical, horizontal, and rotational directions.