A brake system provided with a brake booster using intake negative pressure of an engine for boosting a brake operating force for a vehicle. A requested braking force is detected base on an operating amount of a brake pedal, and when the requested braking force is less than a threshold value, a master cylinder pressure prevailing in the master cylinder using an operating force boosted by the brake booster is supplied to the wheel cylinder. On the other hand, when the requested braking force is greater than or equal to the threshold value, brake fluid pressure having been boosted by a pump is supplied to the wheel cylinder. The threshold value is set to a value that becomes greater the larger the negative pressure inside the brake booster.