Within a container b 2 of a spin coater 1, a rotatable support table 4 for supporting a wafer W and an arm 6 for dropping a chemical liquid onto the wafer W are arranged. Also, the spin coater 1 comprises a gas introducing path 12 for introducing a laminar flow forming gas into the container 2. The gas introducing path 12 has a glass filter 13 provided in an upper part of the container 2, whereas the laminar flow forming gas is introduced into the container 2 by way of the glass filter 13. The container 2 is provided with a wall portion 15 formed so as to continuously spread like a curve downward from a lower end edge part of the glass filter 13. As a consequence, a downflow of the laminar flow forming gas occurs in the whole horizontal section of the region surrounded by the wall portion 15 within the container 2, thereby reliably preventing turbulent flows from occurring.