A scroll-type fluid machine , comprising: a main body unit configured to compress a fluid; and a motor unit configured to drive the main body unit , wherein the main body unit includes a fixed scroll , a revolving scroll , a main body casing , and an autorotation preventing mechanism configured to be held by the revolving scroll and the main body casing and prevent autorotation of the revolving scroll , the motor unit includes a rotor , a stator configured to rotate the rotor , a shaft configured to rotate integrally with the rotor , a motor cover configured to house the rotor and the stator , and a main bearing configured to be fixed in the inside by the motor cover and support the shaft , an eccentric portion is included at a distal end of the shaft , the main body unit and the motor unit are connected via the eccentric portion , the main body casing and the motor cover are fastened with a fastening member , and the motor cover includes a motor casing on an outer side in a radial direction of the shaft and a flange in an opening on the main body unit side of the motor casing , wherein the main body unit and the motor unit are fastened via the flange , characterized in that a fastening position of the main body unit and the motor unit is on an outer side in a radial direction than the autorotation preventing mechanism, an inner side in a radial direction of the flange protrudes to the main body unit side farther than an outer side in the radial direction, and an opening section is provided on the motor unit side of the main body casing , and an area of the opening section is larger than a projection area viewed from an axial direction between the eccentric portion and the flange of the motor unit . a main body unit configured to compress a fluid; and a motor unit configured to drive the main body unit , wherein the main body unit includes a fixed scroll , a revolving scroll , a main body casing , and an autorotation preventing mechanism configured to be held by the revolving scroll and the main body casing and prevent autorotation of the revolving scroll , the motor unit includes a rotor , a stator configured to rotate the rotor , a shaft configured to rotate integrally with the rotor , a motor cover configured to house the rotor and the stator , and a main bearing configured to be fixed in the inside by the motor cover and support the shaft , an eccentric portion is included at a distal end of the shaft , the main body unit and the motor unit are connected via the eccentric portion , the main body casing and the motor cover are fastened with a fastening member , and the motor cover includes a motor casing on an outer side in a radial direction of the shaft and a flange in an opening on the main body unit side of the motor casing , wherein the main body unit and the motor unit are fastened via the flange , characterized in that a fastening position of the main body unit and the motor unit is on an outer side in a radial direction than the autorotation preventing mechanism, an inner side in a radial direction of the flange protrudes to the main body unit side farther than an outer side in the radial direction, and an opening section is provided on the motor unit side of the main body casing , and an area of the opening section is larger than a projection area viewed from an axial direction between the eccentric portion and the flange of the motor unit . <EOS>