According to an embodiment, it provides a brake system comprising a pedal simulator connected to a master cylinder and configured to provide a driver with a pedal feeling upon receiving a hydraulic pressure in accordance with a driver's pedal force, wherein the pedal simulator comprises: a damping housing having an air chamber, installed at a block having a bore communicating with an oil hole connected to the master cylinder, and configured to seal the bore; a reaction force unit configured to provide a pedal reaction force by being compressed by oil introduced through the oil hole; and a check valve disposed in a passage through which the air chamber communicates with the external air.