A substrate holding apparatus that holds a substrate is provided. The apparatus comprises a rotary shaft which rotates about a vertical axis and includes a suction path leading from an upper end of the rotary shaft, and a holding unit which includes a suction hole formed in a rotation center, is fixed at the upper end of the rotary shaft such that the suction hole communicates with the suction path, and holds the substrate by sucking the substrate, wherein a plurality of vent holes for introducing an external gas into a space between the holding unit and the substrate are formed at positions rotationally symmetric with respect to the rotation center of the holding unit with an angle to face a back surface of the substrate placed on the holding unit.