1. A pupil detection apparatus that detects an image of a pupil, comprising: an acquisition section that acquires an actual scale value of a peripheral area including the pupil; a first calculation section that calculates an actual scale prediction value of a pupil diameter; a second calculation section that calculates a target value of resolution on the basis of the calculated actual scale prediction value; a normalization section that calculates a scale-up/scale-down factor on the basis of the calculated target value of the resolution and the actual scale value of the peripheral area, and normalizes an image of the peripheral area on the basis of the calculated scale-up/scale-down factor; and a detection section that detects the image of the pupil from the normalized image of the peripheral area.