A gas supplied from a gas source is exposed to an atmosphere above a liquid surface in a tank saving the liquid and thereafter is supplied around a wafer in a treatment chamber through a gas supply passage and a supply port. The gas supplied around the wafer uniformly flows from around the wafer toward above the center of the wafer and thereafter is discharged from an exhaust port which is formed at the top of the treatment chamber. Meanwhile, with respect to the wafer, heat treatment is performed by a heating mechanism and a predetermined PEB is carried out. The humidified gas is supplied into the treatment chamber, thereby preventing drying in the treatment chamber. Therefore, water in resist is not taken out, resulting in that a required resist pattern can be formed on the wafer.