A method of producing a mask blank has a resist film forming (resist coating) process of dispensing a resist solution containing a resist material and a solvent onto a square-like substrate, and rotating the substrate to spread the dispensed resist solution over the substrate and to dry the resist solution on the substrate, thereby forming a resist film on the substrate. While the substrate is rotated in the resist film forming (resist coating) process, an exhausting member performs an exhausting operation to cause an airflow along an upper surface of the substrate from the center of the substrate towards an outer peripheral portion of the substrate so that a puddle of the resist solution formed at a peripheral end portion of the substrate is prevented from being moved towards the center of the substrate by the rotation of the substrate.