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, the first model including model face parts; a position detection unit that detects positions of image face parts of the face on the basis of a second image from the imaging unit; and a comparison unit that determines whether or not a deviation occurs between the positions of the model face parts in the first model and the positions of corresponding image face parts of the second image 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 with positions of the model face parts updated on the basis of the second image.