To increase load resistance of a pipe passage connection part for a brake device of a hydraulic brake system of a motor vehicle, even if the brake device is made of light metal.

A pipe passage connection part is formed by a pipe passage end part 20 expanded into a hollow conical shape and an accompanying part 15 having a truncated conical shape in a hole 11 of a casing 10 of a brake device. The pipe passage end part 20 is pressed on the accompanying part 15 by a union screw 13. A thin-walled steel sleeve 28 for increasing shape strength of the accompanying part 15 is stored in the accompanying part 15.