A driving concentration level calculating apparatus is provided and includes a controller configured to acquire an acceleration of a traveling vehicle and measure a relative velocity to a preceding vehicle. In addition, noise is removed from the acquired acceleration of the traveling vehicle and from the measured relative velocity to the preceding vehicle. A plurality of correlation values are calculated based on the acceleration of the traveling vehicle and the relative velocity to the preceding vehicle from which noise has been removed. In addition, the controller is configured to detect a time at which a maximum correlation value is calculated as a driving concentration level from among the calculated correlation values.