A coordinate-conversion-parameter determination apparatus comprising: an image capture unit arranged to generate a first image by photographing, when located at a first place, a marker (200; 400) whose position and shape are known, the image capture unit being further arranged to generate a second image by photographing the marker (200; 400) when the image capture unit is located at a second place different from the first place; a marker detector arranged to detect feature points of the marker (200; 400) from each of the first image and the second image; a three-dimensional position determiner arranged to calculate three-dimensional coordinates of each of the feature points of the marker (200; 400) in a camera coordinate system having the first place as a reference, based on a position of the feature point in the first image and a position of the feature point in the second image; and a coordinate-conversion-parameter determiner arranged to calculate coordinate conversion parameters, comprising a matrix R min representing rotational motion components, a matrix T min representing translational motion components and a scale change s, for converting three-dimensional coordinates of the feature points of the marker (200; 400) in the camera coordinate system to three-dimensional coordinates of the feature points in a world coordinate system, wherein the coordinate-conversion-parameter determiner is arranged to calculate, as the coordinate conversion parameters, values of R min, T min and s which minimize an evaluation value E given by E = ∑ i | X i ′ − s ⋅ R min ⋅ X i + T min | 2 by using a singular value decomposition of a covariance matrix based on the feature points in the camera coordinate system and the world coordinate system, where X i denotes the i th feature point in the camera coordinate system and X' i denotes the i th feature point in the world coordinate system. an image capture unit arranged to generate a first image by photographing, when located at a first place, a marker (200; 400) whose position and shape are known, the image capture unit being further arranged to generate a second image by photographing the marker (200; 400) when the image capture unit is located at a second place different from the first place; a marker detector arranged to detect feature points of the marker (200; 400) from each of the first image and the second image; a three-dimensional position determiner arranged to calculate three-dimensional coordinates of each of the feature points of the marker (200; 400) in a camera coordinate system having the first place as a reference, based on a position of the feature point in the first image and a position of the feature point in the second image; and a coordinate-conversion-parameter determiner arranged to calculate coordinate conversion parameters, comprising a matrix R min representing rotational motion components, a matrix T min representing translational motion components and a scale change s, for converting three-dimensional coordinates of the feature points of the marker (200; 400) in the camera coordinate system to three-dimensional coordinates of the feature points in a world coordinate system, wherein the coordinate-conversion-parameter determiner is arranged to calculate, as the coordinate conversion parameters, values of R min, T min and s which minimize an evaluation value E given by E = ∑ i | X i ′ − s ⋅ R min ⋅ X i + T min | 2 by using a singular value decomposition of a covariance matrix based on the feature points in the camera coordinate system and the world coordinate system, where X i denotes the i th feature point in the camera coordinate system and X' i denotes the i th feature point in the world coordinate system.