A displacement magnitude detection device for a vehicle-mounted camera, comprising: a reference value calculating unit which divides, in an image (Im, Im1, Im2) taken by the vehicle-mounted camera with a vertical coordinate (y) and a horizontal coordinate (x), a predetermined region for measurement (Ea1, Ea2) into a plurality of measurement unit regions (D0, D1,..., DN) having a width of a predetermined number of pixels in the vertical direction, and calculates a sum or an average of a luminance value (I(x, y, t)) or a saturation value of pixels inside each measurement unit region (D0, D1,..., DN) as a reference value (re(y, t)) of each measurement unit region (D0, D1,..., DN); wherein the reference value calculating unit sets a vector that shows a first distribution manner (VEC) of the reference values (re(y, t)) in the vertical direction calculated by the reference value calculating unit for a first image taken by the camera at a first imaging time point and also sets a vector that shows a second distribution manner (VEC) of the reference values (re(y, t)) in the vertical direction calculated by the reference value calculating unit for a second image taken by the camera at a second imaging time point different from the first imaging time point; and a camera displacement magnitude calculating unit which calculates the displacement magnitude (Δy) of the camera between the first imaging time point of the first image and the second imaging time point of the second image, on the basis of a shift amount in which the degree of correlation between the first distribution manner (VEC) and the second distribution manner (VEC) becomes the highest, wherein each of the images (Im, Im1, Im2) taken by the camera includes a road in front of the vehicle, and the region for measurement (Eal, Ea2) is set to a region including a vicinity of a horizon far away from the vehicle, and including an image portion of the road, wherein when it is detected that image portions (50, 51) of other vehicles are included in the images (Im, Im1, Im2) taken by the camera, a region for measurement changing unit changes to a region for measurement in which these image portions are removed. a reference value calculating unit which divides, in an image (Im, Im1, Im2) taken by the vehicle-mounted camera with a vertical coordinate (y) and a horizontal coordinate (x), a predetermined region for measurement (Ea1, Ea2) into a plurality of measurement unit regions (D0, D1,..., DN) having a width of a predetermined number of pixels in the vertical direction, and calculates a sum or an average of a luminance value (I(x, y, t)) or a saturation value of pixels inside each measurement unit region (D0, D1,..., DN) as a reference value (re(y, t)) of each measurement unit region (D0, D1,..., DN); wherein the reference value calculating unit sets a vector that shows a first distribution manner (VEC) of the reference values (re(y, t)) in the vertical direction calculated by the reference value calculating unit for a first image taken by the camera at a first imaging time point and also sets a vector that shows a second distribution manner (VEC) of the reference values (re(y, t)) in the vertical direction calculated by the reference value calculating unit for a second image taken by the camera at a second imaging time point different from the first imaging time point; and a camera displacement magnitude calculating unit which calculates the displacement magnitude (Δy) of the camera between the first imaging time point of the first image and the second imaging time point of the second image, on the basis of a shift amount in which the degree of correlation between the first distribution manner (VEC) and the second distribution manner (VEC) becomes the highest, wherein each of the images (Im, Im1, Im2) taken by the camera includes a road in front of the vehicle, and the region for measurement (Eal, Ea2) is set to a region including a vicinity of a horizon far away from the vehicle, and including an image portion of the road, wherein when it is detected that image portions (50, 51) of other vehicles are included in the images (Im, Im1, Im2) taken by the camera, a region for measurement changing unit changes to a region for measurement in which these image portions are removed.