To improve durability of a seal ring sealing a lid member and suppress the total length of a hydraulic master cylinder.

A cylinder hole 8 having a bottom is formed on the one end opening part of a cylinder body 4 opening at both ends by mounting the lid member 7. The lid member 7 is composed of a cylindrical sleeve 5 having the bottom and a plug 6 of larger diameter than the sleeve 5. The sleeve 5 has an inside diameter which a piston 9 can insert into, and an opening side is internally inserted into the cylinder body 4 toward the inside part of the cylinder body 4 through the seal ring 24. The plug is equipped with a male screw part 6a on the outer periphery and a recessed part 6b on the one side surface, The male screw part 6a is screwed on the one side opening part of the cylinder body by directing the recessed part 6b toward the sleeve side 5, and a bottom wall 5c of the sleeve 5 is stored into the recessed part 6b.