A surface treating apparatus that suppresses occurrence of defects is provided. A treatment solution is accumulated in a tank 15 through a treatment solution collecting port/air discharging port 13 in a lower portion of a body 4. An air heated by the treatment solution flows toward an upper portion (portion without the treatment solution) of the tank 15 via the treatment solution collecting port/air discharging port 13 in the lower portion of the body 4, and is discharged via an exhaust duct 17. In this way, the air that is heated and tends to flow upward in the body 4 is discharged from the lower portion thereof and is replaced with an external air from the upper portion thereof. Accordingly, the air in the body 4 can be maintained at a uniform temperature. Thus, the treatment solution that reaches a lower portion of a substrate 54 from an upper portion thereof can be maintained at a uniform temperature. The air is caused to flow toward the lower portion from the upper portion in the body 4, so that the substrate 54 is pulled downward, and swinging of the substrate 54 can thus be reduced. Therefore, the substrate 54 can be less likely to contact an inlet 44 and an outlet 46.