An apparatus for fabricating a substrate includes a chamber providing a space in which processes are performed, a contaminant measurement substrate including a base material configured to collect contaminants, and laser marks on the base material and defining coordinates of the base material, a first stage disposed inside the chamber, and upon which the contaminant measurement substrate is seated during collection of the contaminants of the chamber, a second stage disposed outside the chamber, and upon which the contaminant measurement substrate is seated during measurement of the contaminants of the chamber collected on the contaminant measurement substrate, and a contaminant measurement light source disposed on an upper portion of the second stage and configured to irradiate the contaminant measurement substrate seated on the second stage with light during the measurement of the contaminants of the chamber collected on the contaminant measurement substrate.