An in-vehicle camera posture detecting apparatus includes a first image storing unit configured to store an image of a calibration sheet placed near the vehicle, the calibration sheet having a plurality of calibration marks, a first posture estimating unit for estimating the posture of the camera based on the first image, a second image storing unit that stores an image of the calibration sheet after movement of the vehicle, a second posture estimating unit that estimates the posture of the camera based on the second image, a sheet deviation calculating unit that calculates an amount of deviation of the calibration sheet from a predetermined position based on the estimates provided by the first and second posture estimating units, and a camera posture determining unit that determines the posture of the camera based on a posture estimated value and the calculated amount of deviation.