A surface inspection apparatus, comprising a wafer table rotated by a motor, a pair of clamp arms rotatably mounted with respect to the wafer table, pushing means for pushing the clamp arms so as to rotate in the direction toward the center, positioning seats in arcuate shape mounted on the wafer table where a peripheral portion of a wafer is placed, and clamp pawls in arcuate shape coming into contact with a peripheral edge of the wafer, wherein the clamp arms are rotated around positions which are different from the rotation center of the motor, the clamp pawls are separated from the positioning seats when the clamp arm is rotated on a position opposite to the center, and the peripheral edge of the wafer is clamped between the positioning seats and the clamp pawls when the clamp arm is in clamping condition.