PURPOSE: To dispense with the diverseified specifications of an operating pressure lead-in pipe member and facilitate compact constitution so as to improve the space factor of layout space, and moreover dispense with the mounting work of a member for clamping a hose to the pipe member.

CONSTITUTION: One end part 11a of an operating pressure supply hose 11 is connected to an operating pressure lead-in pipe member 9 fitted to the outer face side of the casing 2 of a brake booster body part 3, and operating pressure is supplied to a pressure chamber 6 in the casing 2 through the hose 11 and the pipe member 9. In a brake booster 1 of such constitution, the casing 2 is provided with a recessed part 8 recessed toward the interior side, and the pipe member 9 is fitted to the outer face side (outer side face 8a) of the recessed part 8 in the state of the center hole 9a of the pipe member 9 being communicated with an operating pressure lead-in hole formed at the recessed part 8.