Disclosed herein is an apparatus for detecting a passenger and wearing seat belt based on an image, which includes an image detector configured to detect an image of an interior of a vehicle, which is captured using a camera, a controller configured to analyze the image of the interior of the vehicle, which is captured through the image detector, and determine whether a passenger is present and whether the passenger wears a seat belt, and an information output part configured to output a warning or an alarm according to discrimination of the passenger from an object, which is determined by the controller, the presence or absence of the passenger, and whether the passenger wears the seat belt.