1. A face detection apparatus detecting a face from an image which includes the face of a target person in a region imaged by an imaging unit, the apparatus comprising: a model fitting unit that generates a first model of the face on the basis of a first image from the imaging unit; a tracking unit that fits the first model to a second image from the imaging unit; a position detection unit that detects positions of face parts of the face on the basis of the second image; and a comparison unit that determines whether or not a deviation occurs between the positions of the face parts in the first model fitted by the tracking unit and the positions of the face parts detected by the position detection unit, wherein, when the comparison unit determines that the deviation occurs, the model fitting unit generates a second model of the face on the basis of the second image.