PURPOSE: To adhere a self-adherent sheet even to an object to be adhered in which its junction surface is rough.

CONSTITUTION: A self-adherent sheet 1 is brought into contact with the junction surface 11 of an object 10 to be adhered by an adherent film 2, and placed on the object 10. An ultrasonic vibration tool 30 is disposed on the sheet 1, and ultrasonic vibration is applied to the sheet 1 while pushing the sheet 1 and the object 10 under a predetermined pressure by the tool 30. The film 2 is melted, its molten resin flows into fine recesses formed on the surface 11 of the object 10 to be adhered. Thus, the sheet 1 is adhered to the object 10.