A turbocharger comprising: a turbine including a turbine shaft; and a compressor including a compressor impeller fitted to one end side of the turbine shaft, the turbine shaft comprising: a turbine impeller of the turbine; a rotor shaft joined on the other end side to the turbine impeller, and an axial force receiving part being formed at a position abutting an end surface on a side of a back surface of the compressor impeller, wherein the rotor shaft includes: a fitting region configured to fit with the compressor impeller of the compressor by inserting the one end side of the rotor shaft into a through hole formed in the compressor impeller, wherein the through hole of the compressor impeller has the same diameter in an axial direction; a fastening region formed between the fitting region and the one end side of the rotor shaft, and configured to allow fastening by a fastening part; and a tapered part having a maximum outer diameter at a position closest to the turbine impeller in the fitting region and formed such that an outer diameter of the rotor shaft decreases from the position closest to the turbine impeller toward a tip side of the compressor impeller, characterized in that an entirety of the fitting region and an inner surface of the through hole are in contact with each other, when the compressor impeller is mounted on the turbine shaft, and wherein the tapered part is constituted by an entirely tapered part formed over the entirety of the fitting region. a turbine including a turbine shaft; and a compressor including a compressor impeller fitted to one end side of the turbine shaft, the turbine shaft comprising: a turbine impeller of the turbine; a rotor shaft joined on the other end side to the turbine impeller, and an axial force receiving part being formed at a position abutting an end surface on a side of a back surface of the compressor impeller, a turbine impeller of the turbine; a rotor shaft joined on the other end side to the turbine impeller, and an axial force receiving part being formed at a position abutting an end surface on a side of a back surface of the compressor impeller, wherein the rotor shaft includes: a fitting region configured to fit with the compressor impeller of the compressor by inserting the one end side of the rotor shaft into a through hole formed in the compressor impeller, wherein the through hole of the compressor impeller has the same diameter in an axial direction; a fastening region formed between the fitting region and the one end side of the rotor shaft, and configured to allow fastening by a fastening part; and a tapered part having a maximum outer diameter at a position closest to the turbine impeller in the fitting region and formed such that an outer diameter of the rotor shaft decreases from the position closest to the turbine impeller toward a tip side of the compressor impeller, characterized in that an entirety of the fitting region and an inner surface of the through hole are in contact with each other, when the compressor impeller is mounted on the turbine shaft, and a fitting region configured to fit with the compressor impeller of the compressor by inserting the one end side of the rotor shaft into a through hole formed in the compressor impeller, wherein the through hole of the compressor impeller has the same diameter in an axial direction; a fastening region formed between the fitting region and the one end side of the rotor shaft, and configured to allow fastening by a fastening part; and a tapered part having a maximum outer diameter at a position closest to the turbine impeller in the fitting region and formed such that an outer diameter of the rotor shaft decreases from the position closest to the turbine impeller toward a tip side of the compressor impeller, characterized in that an entirety of the fitting region and an inner surface of the through hole are in contact with each other, when the compressor impeller is mounted on the turbine shaft, and wherein the tapered part is constituted by an entirely tapered part formed over the entirety of the fitting region.