A calculation device (14, 37, 57) comprising a controller (16, 38, 59) configured to extract, from a captured image of a subject, a plurality of lines (103R, 103L, 104R, 104L) corresponding to straight lines (103, 104) located on a plane and parallel to each other in the subject, and to calculate first calibration data so that mapping lines (107R, 107L, 108R, 108L) obtained when the extracted plurality of lines (103R, 103L, 104R, 104L) are mapped to a three-dimensional coordinate space are parallel to each other, wherein the controller (16, 38, 59) is configured to: map the plurality of lines (103R, 103L, 104R, 104L) to the three-dimensional coordinate space when calculating the first calibration data; calculate the first calibration data so that the mapping lines (107R, 107L, 108R, 108L) obtained as a result of the mapping are parallel to each other; and calibrate an angle (θ CL, θ CL) between an optical axis of a camera (11, 12, 31, 32, 51, 52) that captures the image and the plane, based on the first calibration data, characterized in that the controller (16, 38, 59) is further configured to: calculate the first calibration data for each of a plurality of captured images of the same subject, the plurality of images having parallax therebetween: calculate second calibration data by comparing corresponding mapping lines (107R, 107L, 108R, 108L) in the plurality of images; and perform calibration for a parallax deviation (Δu) between a plurality of cameras (11, 12, 31, 32, 51, 52) that captures the plurality of images, based on the second calibration data, the parallax deviation being the difference of positional deviation between the plurality of cameras occurring with time. map the plurality of lines (103R, 103L, 104R, 104L) to the three-dimensional coordinate space when calculating the first calibration data; calculate the first calibration data so that the mapping lines (107R, 107L, 108R, 108L) obtained as a result of the mapping are parallel to each other; and calibrate an angle (θ CL, θ CL) between an optical axis of a camera (11, 12, 31, 32, 51, 52) that captures the image and the plane, based on the first calibration data, characterized in that the controller (16, 38, 59) is further configured to: calculate the first calibration data for each of a plurality of captured images of the same subject, the plurality of images having parallax therebetween: calculate second calibration data by comparing corresponding mapping lines (107R, 107L, 108R, 108L) in the plurality of images; and perform calibration for a parallax deviation (Δu) between a plurality of cameras (11, 12, 31, 32, 51, 52) that captures the plurality of images, based on the second calibration data, the parallax deviation being the difference of positional deviation between the plurality of cameras occurring with time. calculate the first calibration data for each of a plurality of captured images of the same subject, the plurality of images having parallax therebetween: calculate second calibration data by comparing corresponding mapping lines (107R, 107L, 108R, 108L) in the plurality of images; and perform calibration for a parallax deviation (Δu) between a plurality of cameras (11, 12, 31, 32, 51, 52) that captures the plurality of images, based on the second calibration data, the parallax deviation being the difference of positional deviation between the plurality of cameras occurring with time.