Braking device for vehicle

A braking device for a vehicle, comprising:

• a cylinder;
• a master piston provided inside the cylinder while being allowed to be slidably movable therein in an axial direction and having a pressure applying piston portion defining a master chamber, in which a brake fluid is pressurized, with an inner circumferential surface of the cylinder, and a servo pressure receiving portion defining a servo pressure chamber with the inner circumferential surface of the cylinder;
• an input piston arranged inside of the cylinder at a rear-side thereof while being allowed to be slidably movable in the axial direction and to be distanced away from a rear end surface of the master piston for a predetermined distance;
• a pressure accumulating device accumulating a pressure of the brake fluid;
• a pilot pressure generating device generating a pilot pressure corresponding to an operation amount of the input piston by using the brake fluid of the pressure accumulating device;
• and
• a regulator having a first piston fitted into a housing while being allowed to be slidably movable therein and dividing an inside of the housing into a first pilot chamber in communication with the pilot pressure generating device and a servo pressure generating chamber in communication with the servo pressure chamber, a valve mechanism that is configured to connect the servo pressure generating chamber with the pressure accumulating device or a reservoir in response to a movement of the first piston, and a second piston fitted into the housing while being allowed to contact and detach from the first piston and dividing the inside of the housing into the first pilot chamber and a second pilot chamber in communication with the master chamber, wherein
• the second piston is formed so that an end surface thereof exposed to the first pilot chamber has a larger pressure-receiving surface area than an end surface exposed to the second pilot chamber.