A driving device (20, 20') for a turbocharger comprising: a shaft; and a cylindrical bush having an insertion hole into which the shaft can be inserted, the insertion hole including an opening portion having an inner diameter decreasing from a first end surface toward a second end surface of the bush, and a small-diameter hole portion extending from an end of the opening portion to the second end surface, the shaft including a shaft portion having an outer diameter smaller than an inner diameter of the small-diameter hole portion, and an abutment portion having an outer diameter greater than the inner diameter of the small-diameter hole portion, the bush having a sealing surface of truncated cone shape configured as a surface extending obliquely inward from an inner peripheral edge of the first end surface to the end of the opening portion, a gap is formed between the small-diameter hole portion and the shaft portion of the shaft inside the small-diameter hole portion for preventing adhesion or galling of a valve apparatus, wherein the driving device (20, 20') is configured such that the abutment portion of the shaft abuts on the sealing surface of the bush in an axial direction of the insertion hole so as to seal the gap is formed between the small-diameter hole portion and the shaft portion inside the insertion hole, characterized in that the abutment portion has an elliptical spherical shape having a major axis perpendicular or parallel to the axial direction of the insertion hole; and the small-diameter hole portion is formed with a constant inner diameter from the end (5a1) to the second end surface. a shaft; and a cylindrical bush having an insertion hole into which the shaft can be inserted, the insertion hole including an opening portion having an inner diameter decreasing from a first end surface toward a second end surface of the bush, and a small-diameter hole portion extending from an end of the opening portion to the second end surface, the shaft including a shaft portion having an outer diameter smaller than an inner diameter of the small-diameter hole portion, and an abutment portion having an outer diameter greater than the inner diameter of the small-diameter hole portion, the bush having a sealing surface of truncated cone shape configured as a surface extending obliquely inward from an inner peripheral edge of the first end surface to the end of the opening portion, a gap is formed between the small-diameter hole portion and the shaft portion of the shaft inside the small-diameter hole portion for preventing adhesion or galling of a valve apparatus, wherein the driving device (20, 20') is configured such that the abutment portion of the shaft abuts on the sealing surface of the bush in an axial direction of the insertion hole so as to seal the gap is formed between the small-diameter hole portion and the shaft portion inside the insertion hole, characterized in that the abutment portion has an elliptical spherical shape having a major axis perpendicular or parallel to the axial direction of the insertion hole; and the small-diameter hole portion is formed with a constant inner diameter from the end (5a1) to the second end surface.