A rotary machine comprising: a casing having first and second casing half-bodies abutting each other via an abutting surface therebetween, a first flange which is a part of the first casing half-body extending along the abutting surface and in which a first hole portion is formed, and a second flange which is a part of the second casing half-body extending along the abutting surface and in which a second hole portion corresponding to the first hole portion is formed; and a first bolt inserted into the first and second hole portions (610, 611) and fastened to a first female screw (Sf) formed in at least a part of the second hole portion, wherein the first hole portion is passed through the first flange, the second hole portion is formed to be shallower in depth than the thickness of the second flange, the second flange has a first portion which is thicker than the first flange in a direction in which the second hole portion extends, and the second hole portion is formed in the first portion, characterized in that the second flange has a second portion which is thinner than the first portion around the first portion, a third hole portion passing through a portion of the first flange corresponding to the second portion is formed in the first flange, a fourth hole portion corresponding to the third hole portion, which is shallower in depth than the thickness of the second portion, is formed in the second portion, a second female screw (Sf) being formed in at least a part of the fourth hole portion, the rotary machine further includes a second bolt inserted into the third and fourth hole (610B, 611B) portions and fastened to the second female screw (Sf), and the first female screw (Sf) is formed at a position deeper than the thickness of the first flange with respect to the abutting surface of the second casing half body. a casing having first and second casing half-bodies abutting each other via an abutting surface therebetween, a first flange which is a part of the first casing half-body extending along the abutting surface and in which a first hole portion is formed, and a second flange which is a part of the second casing half-body extending along the abutting surface and in which a second hole portion corresponding to the first hole portion is formed; and a first bolt inserted into the first and second hole portions (610, 611) and fastened to a first female screw (Sf) formed in at least a part of the second hole portion, wherein the first hole portion is passed through the first flange, the second hole portion is formed to be shallower in depth than the thickness of the second flange, the second flange has a first portion which is thicker than the first flange in a direction in which the second hole portion extends, and the second hole portion is formed in the first portion, characterized in that the second flange has a second portion which is thinner than the first portion around the first portion, a third hole portion passing through a portion of the first flange corresponding to the second portion is formed in the first flange, a fourth hole portion corresponding to the third hole portion, which is shallower in depth than the thickness of the second portion, is formed in the second portion, a second female screw (Sf) being formed in at least a part of the fourth hole portion, the rotary machine further includes a second bolt inserted into the third and fourth hole (610B, 611B) portions and fastened to the second female screw (Sf), and the first female screw (Sf) is formed at a position deeper than the thickness of the first flange with respect to the abutting surface of the second casing half body.