MASTER CYLINDER FOR ELECTRONIC BRAKE SYSTEM

Provided is a master cylinder for an electronic brake system. The master cylinder for the electronic brake system includes a pedal simulator provided between a first master piston and a second master piston and having a rubber member that provides reaction force to a brake pedal, and the first master piston includes a first piston and a second piston coupled to be movable relative to each other and having a communication channel to allow a pressing medium to flow between a reservoir and a first master chamber, a communication channel sealing member configured to block a portion of the communication channel according to a relative movement of the first piston and the second piston, and an elastic member configured to provide elastic force in a direction in which the first piston and the second piston are spaced apart.