A throttle valve unit is disclosed that includes a main body having a cylinder portion defining a fluid passage. The main body also includes a fastening portion projecting from an outer peripheral surface of the cylinder portion for fastening to a separate member. The cylinder portion defines an axis. The throttle valve unit also includes a throttle valve that is rotatably supported by the cylinder portion for opening and closing the fluid passage. The throttle valve is supported by the cylinder portion at a support area. The fastening portion is provided at approximately the same axial position relative to the axis as the support area of the throttle valve and includes a plurality of mounting portions for coupling to the separate member and a plurality of connecting portions extending between the mounting portions.