Hydraulic master cylinder apparatus for vehicle with bar handle

A hydraulic master cylinder apparatus for a vehicle with a bar handle has: a master cylinder (4) having the center axis (6) of a cylinder body (7) having a cylinder hole (8); an operation lever (5) pivotally supported on the cylinder body (7); a push rod (6) interposed between the operation lever (5) and a piston (12), the operation lever (5) being divided into a lever main body (25) and a knocker (26); and a stop lamp switch (31) disposed on the cylinder body (7); characterized in that, in the knocker (26), there is formed a switch press portion (26e) for actuating the operation piece of the stop lamp switch (31) with the rotation of the operation lever (5).