A turbocharger comprising: an impeller; a rotary shaft to which the impeller is attached; and a bearing structure that supports the rotary shaft, wherein the rotary shaft comprises a small diameter portion (4b, 4b'), a large diameter portion, and a step part connecting the small diameter portion (4b, 4b') to the large diameter portion, wherein the bearing structure comprises: a sleeve (32, 32') provided so as to surround an outer circumference of the rotary shaft that rotates about a center axis line and configured to rotate together with the rotary shaft; collars (34a, 34b) provided so as to abut against both ends in the center axis line direction of the sleeve (32, 32'), respectively, having a larger diameter than the sleeve (32, 32'), and configured to rotate together with the rotary shaft; and a bearing (12, 12') arranged on an outer circumference side of the sleeve (32, 32') and between the collars (34a, 34b), wherein the bearing (12, 12') is suitable for functioning as a journal bearing that supports the rotary shaft in a radial direction via the sleeve (32, 32') and is suitable for functioning as a thrust bearing that supports the rotary shaft in a thrust direction via the collars (34a, 34b), wherein the sleeve and the collars (34a, 34b) are provided on the small diameter portion (4b, 4b'), and wherein one of the collars on the large diameter portion side is provided so as to abut against the step part, wherein the turbocharger further comprises: a fastener that is attached to an end of the rotary shaft on the small diameter portion (4b, 4b') side and presses the collars (34a, 34b) and the sleeve (32, 32') toward the step part side; and a journal bearing provided on the large diameter portion, wherein the sleeve has substantially the same outer diameter as the large diameter portion. an impeller; a rotary shaft to which the impeller is attached; and a bearing structure that supports the rotary shaft, wherein the rotary shaft comprises a small diameter portion (4b, 4b'), a large diameter portion, and a step part connecting the small diameter portion (4b, 4b') to the large diameter portion, wherein the bearing structure comprises: a sleeve (32, 32') provided so as to surround an outer circumference of the rotary shaft that rotates about a center axis line and configured to rotate together with the rotary shaft; collars (34a, 34b) provided so as to abut against both ends in the center axis line direction of the sleeve (32, 32'), respectively, having a larger diameter than the sleeve (32, 32'), and configured to rotate together with the rotary shaft; and a bearing (12, 12') arranged on an outer circumference side of the sleeve (32, 32') and between the collars (34a, 34b), a sleeve (32, 32') provided so as to surround an outer circumference of the rotary shaft that rotates about a center axis line and configured to rotate together with the rotary shaft; collars (34a, 34b) provided so as to abut against both ends in the center axis line direction of the sleeve (32, 32'), respectively, having a larger diameter than the sleeve (32, 32'), and configured to rotate together with the rotary shaft; and a bearing (12, 12') arranged on an outer circumference side of the sleeve (32, 32') and between the collars (34a, 34b), wherein the bearing (12, 12') is suitable for functioning as a journal bearing that supports the rotary shaft in a radial direction via the sleeve (32, 32') and is suitable for functioning as a thrust bearing that supports the rotary shaft in a thrust direction via the collars (34a, 34b), wherein the sleeve and the collars (34a, 34b) are provided on the small diameter portion (4b, 4b'), and wherein one of the collars on the large diameter portion side is provided so as to abut against the step part, wherein the turbocharger further comprises: a fastener that is attached to an end of the rotary shaft on the small diameter portion (4b, 4b') side and presses the collars (34a, 34b) and the sleeve (32, 32') toward the step part side; and a journal bearing provided on the large diameter portion, a fastener that is attached to an end of the rotary shaft on the small diameter portion (4b, 4b') side and presses the collars (34a, 34b) and the sleeve (32, 32') toward the step part side; and a journal bearing provided on the large diameter portion, wherein the sleeve has substantially the same outer diameter as the large diameter portion.