A sleepiness sign detection apparatus, comprising: a head movement detection unit configured to detect a head movement; an eye movement detection unit configured to detect an eye movement; an ideal eye movement angular velocity calculation unit configured to calculate an ideal eye movement angular velocity based on a head movement data detected by the head movement detection unit; an eye-rotation angular velocity calculation unit configured to calculate an eye-rotation angular velocity based on an eye movement data detected by the eye movement detection unit; and a sleepiness sign detection unit configured to detect vestibule-ocular reflex from the ideal eye movement angular velocity and the eye-rotation angular velocity, and determine a sign of sleepiness based on the vestibule-ocular reflex, wherein the sleepiness sign detection unit is configured to calculate a VOR gain defined by G, characterized in that the sleepiness sign detection unit is furthermore configured to calculate a decrease rate of the VOR gain, and/or an approximation residual defined by e(t) and a residual standard deviation, the G and/or e( t), respectively, obtained by approximating the eye-rotation angular velocity by a linear equation of the ideal eye movement angular velocity: e t = G ⋅ h t − τ + dc + ε t, where e(t) represents eye-rotation angular velocity; G represents VOR gain; h(t) represents ideal eye movement angular velocity; τ represents delay time of eye movement with respect to head movement; dc represents constant term; and ε(t) represents residual of regression model, and to determine a sign of sleepiness, when the decrease rate of the VOR gain and/or an increase rate of the residual standard deviation, respectively, exceeds a threshold value set in advance. a head movement detection unit configured to detect a head movement; an eye movement detection unit configured to detect an eye movement; an ideal eye movement angular velocity calculation unit configured to calculate an ideal eye movement angular velocity based on a head movement data detected by the head movement detection unit; an eye-rotation angular velocity calculation unit configured to calculate an eye-rotation angular velocity based on an eye movement data detected by the eye movement detection unit; and a sleepiness sign detection unit configured to detect vestibule-ocular reflex from the ideal eye movement angular velocity and the eye-rotation angular velocity, and determine a sign of sleepiness based on the vestibule-ocular reflex, wherein the sleepiness sign detection unit is configured to calculate a VOR gain defined by G, characterized in that the sleepiness sign detection unit is furthermore configured to calculate a decrease rate of the VOR gain, and/or an approximation residual defined by e(t) and a residual standard deviation, the G and/or e( t), respectively, obtained by approximating the eye-rotation angular velocity by a linear equation of the ideal eye movement angular velocity: e t = G ⋅ h t − τ + dc + ε t, where e(t) represents eye-rotation angular velocity; G represents VOR gain; h(t) represents ideal eye movement angular velocity; τ represents delay time of eye movement with respect to head movement; dc represents constant term; and ε(t) represents residual of regression model, and to determine a sign of sleepiness, when the decrease rate of the VOR gain and/or an increase rate of the residual standard deviation, respectively, exceeds a threshold value set in advance.