A detection device, comprising: a deformation detection unit to detect a crack on a surface of a structure from image information on the structure; a step detection unit to detect a step on the surface of the structure from three-dimensional point group information on the structure measured with a laser; and a determination unit to determine a state of the crack using information on the crack generated by the deformation detection unit and information on the step generated by the step detection unit; wherein the deformation detection unit includes: a deformation extraction unit to extract the crack on the surface of the structure from the image information; and a deformation vector information generation unit to generate vector information on the extracted crack using the three-dimensional point group information on the surface of the structure, wherein a deformation vector is a succession of contiguous line segments between two end points and vector information comprises the positions of the two end points and of the plurality of segments, the step detection unit includes: a step extraction unit to extract the step on the surface of the structure from the three-dimensional point group information; and a step vector information generation unit to generate vector information on the extracted step, wherein a step vector is a succession of contiguous line segments between two end points and vector information comprises the positions of the two end points and of the plurality of segments; the determination unit determines the state of the crack using the vector information on the crack and the vector information on the step, by calculating an inter-segment distance between each line segment of the vector indicated by the vector information on the crack and a line segment, nearest to the each line segment, of the vector indicated by the vector information on the step, and determining a state of the crack on the basis of the ratio of points of the vector information on the crack having the inter-segment distance to the vector information on the corresponding step less than a specified threshold value. a deformation detection unit to detect a crack on a surface of a structure from image information on the structure; a step detection unit to detect a step on the surface of the structure from three-dimensional point group information on the structure measured with a laser; and a determination unit to determine a state of the crack using information on the crack generated by the deformation detection unit and information on the step generated by the step detection unit; wherein the deformation detection unit includes: a deformation extraction unit to extract the crack on the surface of the structure from the image information; and a deformation vector information generation unit to generate vector information on the extracted crack using the three-dimensional point group information on the surface of the structure, wherein a deformation vector is a succession of contiguous line segments between two end points and vector information comprises the positions of the two end points and of the plurality of segments, a deformation extraction unit to extract the crack on the surface of the structure from the image information; and a deformation vector information generation unit to generate vector information on the extracted crack using the three-dimensional point group information on the surface of the structure, wherein a deformation vector is a succession of contiguous line segments between two end points and vector information comprises the positions of the two end points and of the plurality of segments, the step detection unit includes: a step extraction unit to extract the step on the surface of the structure from the three-dimensional point group information; and a step vector information generation unit to generate vector information on the extracted step, wherein a step vector is a succession of contiguous line segments between two end points and vector information comprises the positions of the two end points and of the plurality of segments; a step extraction unit to extract the step on the surface of the structure from the three-dimensional point group information; and a step vector information generation unit to generate vector information on the extracted step, wherein a step vector is a succession of contiguous line segments between two end points and vector information comprises the positions of the two end points and of the plurality of segments; the determination unit determines the state of the crack using the vector information on the crack and the vector information on the step, by calculating an inter-segment distance between each line segment of the vector indicated by the vector information on the crack and a line segment, nearest to the each line segment, of the vector indicated by the vector information on the step, and determining a state of the crack on the basis of the ratio of points of the vector information on the crack having the inter-segment distance to the vector information on the corresponding step less than a specified threshold value.