According to the invention, a chemically adsorbing material (1) is reacted with a substrate (4) surface having active hydrogen groups by dipping the substrate (4) into a solution (2) of the chemically adsorbing material (1) simultaneous and applying ultrasonic waves to the solution (2) by an ultrasonic washer (3). In this way, a high concentration monomolecular and/or polymer film (5) substantially free from pin holes can be formed in a short period of time. That is, while the ultrasonic waves are applied, a chemical adsorbing material (1) having an end functional chlorosilyl group is adsorbed onto the substrate surface (4), thereby forming a chemically adsorbed monomolecular and/or polymer film (5). The frequency of the ultrasonic waves are suitably in a range of 25 to 50 kHz. In addition, after formation of the adsorbed film (5), the substrate (4) is washed for making monomolecular film by dipping it in a washing solution while applying ultrasonic waves. In this way, non-reacted chemical adsorbing material (1) remaining on the substrate (4) can be efficiently washed away.