A turbo machine comprising: a rotation shaft that comprises a first taper portion and a first cylinder portion , the first taper portion decreasing in diameter toward one end of the rotation shaft , the first cylinder portion being constant in diameter in an axial direction of the rotation shaft ; a first impeller that is fixed to the rotation shaft and that is used for compressing or expanding working fluid; a first bearing that rotatably supports the first taper portion and the first cylinder portion ; a second bearing that is positioned on an opposite side of the first impeller from the first bearing in the axial direction of the rotation shaft and that supports the rotation shaft both in the axial direction and a radial direction of the rotation shaft, a second taper portion that is located on the opposite side of the first impeller from the first bearing in the axial direction of the rotation shaft and that decreases in diameter toward the other end of the rotation shaft , and a second cylinder portion that is constant in diameter, wherein the second bearing rotatably supports the second taper portion and the second cylinder portion on the opposite side of the first impeller from the first bearing , characterized in that the turbo machine satisfies a formula (B): C 1 + C 2 > C 3 + C 4 wherein C1 is an average clearance between the first taper portion and the first bearing in a direction perpendicular to an outer surface of the first taper portion , C2 is an average clearance between the second taper portion and the second bearing in the direction perpendicular to the outer surface of the second taper portion , C3 is an average clearance between the first cylinder portion and the first bearing , and C4 is an average clearance between the second cylinder portion and the second bearing . a rotation shaft that comprises a first taper portion and a first cylinder portion , the first taper portion decreasing in diameter toward one end of the rotation shaft , the first cylinder portion being constant in diameter in an axial direction of the rotation shaft ; a first impeller that is fixed to the rotation shaft and that is used for compressing or expanding working fluid; a first bearing that rotatably supports the first taper portion and the first cylinder portion ; a second bearing that is positioned on an opposite side of the first impeller from the first bearing in the axial direction of the rotation shaft and that supports the rotation shaft both in the axial direction and a radial direction of the rotation shaft, a second taper portion that is located on the opposite side of the first impeller from the first bearing in the axial direction of the rotation shaft and that decreases in diameter toward the other end of the rotation shaft , and a second cylinder portion that is constant in diameter, wherein the second bearing rotatably supports the second taper portion and the second cylinder portion on the opposite side of the first impeller from the first bearing , characterized in that the turbo machine satisfies a formula (B): C 1 + C 2 > C 3 + C 4 wherein C1 is an average clearance between the first taper portion and the first bearing in a direction perpendicular to an outer surface of the first taper portion , C2 is an average clearance between the second taper portion and the second bearing in the direction perpendicular to the outer surface of the second taper portion , C3 is an average clearance between the first cylinder portion and the first bearing , and C4 is an average clearance between the second cylinder portion and the second bearing . <EOS>