Provided is a pupil hidden state detecting apparatus which can detect directly a hidden state of a pupil without detecting a hiding object. The pupil hidden state detecting apparatus 20 is comprises: a visual line direction detecting section 22 operable to detect a direction of a visual line of a driver； a brightness gradient calculating section 23 operable to calculate a brightness gradient of an image of an eye area； a gradient intensity calculating section 24 operable to calculate a gradient intensity vertical distribution ； a gradient intensity storing section 25 adapted to store therein the data of a reference gradient intensity vertical distribution under the state that the direction of the visual line of the driver is toward an instrument panel； a difference calculating section 26 operable to calculate a difference between the gradient intensity vertical distribution of the current frame and the reference gradient intensity vertical distribution； an evaluation value calculating section 27 operable to calculate an evaluation value indicating a degree of possibility that the pupil of the driver is hidden； and a pupil hidden judging section 29 operable to judge that the pupil is hidden, when the evaluation values indicative of the pupil being hidden is continued.
