Method for producing buffer layer and cbd film-forming apparatus

[Problem] To make a CBD film-forming apparatus that does not dissolve a substrate even when the substrate contains a section that does dissolve in a CBD solution. [Solution] A CBD film-forming apparatus is provided with: a supporting/heating unit (3) for supporting a substrate (2) from the rear surface thereof and heating the same; a reaction tank (4) that has an opening (4a) and is for supplying a CBD reaction solution for film forming to the front surface of the substrate (2) supported by the supporting/heating unit (3); and a reaction tank advancement/reversal drive unit capable of advancing the reaction tank (4) toward the front surface of the substrate (2) supported by the supporting/heating unit (3), pressing the opening (4a) against the front surface of the substrate (2), reversing the reaction tank (4) away from the front surface of the substrate (2), and pulling the opening (4a) away from the front surface of the substrate (2).