An apparatus for detecting an alcohol component of a driver's breath includes an inlet that absorbs a driver's exhalation and a passenger's exhalation, respectively, a sensor that detects an alcohol component in the driver's exhalation or the passenger's exhalation, a driver valve controlled to be opened or closed to allow the driver's exhalation to be introduced into the sensor and a passenger valve controlled to be opened or closed to allow the passenger's exhalation to be introduced into the sensor, and a controller that determines whether a passenger is on board a vehicle and controls the driver valve and the passenger valve to be open or closed based on a determination result. Therefore, the driver's breath is distinguished from the passenger's breath and the influence of the passenger is removed to detect the alcohol component in the driver's breath, thereby accurately determining the driver's drinking state.