A substrate supporting unit includes a supporter for supporting a substrate, and a temperature controller for controlling the supporter. The supporter includes liquid supply openings opened at a top surface of the supporter. A liquid is supplied between the substrate and the supporter through the liquid supply opening. Liquid discharge grooves are formed in the top surface of the supporter near the liquid supply openings, and the liquid between the substrate and the supporter is discharged through the liquid discharge grooves. Liquid discharge openings are opened in the liquid discharge grooves, and the liquid is discharged through the liquid discharge openings. Further, the supporter includes exhaust grooves formed in the top surface of the supporter and exhaust openings opened in the exhaust grooves, the exhaust grooves and the exhaust openings also serving as the liquid discharge grooves and the liquid discharge openings, respectively.