A measuring apparatus (100; 200; 500; 600) for measuring a planar relative motion between a tool attacher (110; 210) and a work attacher (120; 220) of a machine tool (150; 250; 550; 650), comprising: an image capturer (101; 201; 501) that includes at least one image capturing element capable of performing image capturing, in the same direction, at a first position (111; 311; 511), a second position (112; 312; 512), and a third position (113; 313; 513), which are not located on the same line, in a state in which said image capturer (101; 201; 501) is attached to one of the tool attacher (110; 210) and the work attacher (120; 220), any one of the first position (111; 311; 511), the second position (112; 312; 512), and the third position (113; 313; 513) being not located on a line that passes through remaining two; an image capturing controller (102; 302) that is configured to cause the image capturing elements at the first position (111; 311; 511), the second position (112; 312; 512), and the third position (113; 313; 513) to capture a first point (121; 321), a second point (122; 322), and a third point (123; 323), respectively, arranged on at least one plane of an XY-plane, an XZ-plane, and a YZ-plane without changing a relative position of one of the tool attacher (110; 210) and the work attacher (120; 220) to which said image capturer (101; 201; 501) is attached, and to change the relative position of one of the tool attacher (110; 210) and the work attacher (120; 220), to cause the image capturing element at the second position (112; 312; 512) and the image capturing element at the third position (113; 313; 513) to capture the first point (121; 321), to cause the image capturing element at the first position (111; 311; 511) and the image capturing element at the third position (113; 313; 513) to capture the second point (122; 322), and to cause the image capturing element at the first position and the image capturing element at the second position to capture the third point (123; 323); and a calculator (103; 303) that is configured to calculate a value indicating the planar relative motion between the tool attacher (110; 210) and the work attacher (120; 220) based on an image capturing result of said image capturer (101; 201; 501). an image capturer (101; 201; 501) that includes at least one image capturing element capable of performing image capturing, in the same direction, at a first position (111; 311; 511), a second position (112; 312; 512), and a third position (113; 313; 513), which are not located on the same line, in a state in which said image capturer (101; 201; 501) is attached to one of the tool attacher (110; 210) and the work attacher (120; 220), any one of the first position (111; 311; 511), the second position (112; 312; 512), and the third position (113; 313; 513) being not located on a line that passes through remaining two; an image capturing controller (102; 302) that is configured to cause the image capturing elements at the first position (111; 311; 511), the second position (112; 312; 512), and the third position (113; 313; 513) to capture a first point (121; 321), a second point (122; 322), and a third point (123; 323), respectively, arranged on at least one plane of an XY-plane, an XZ-plane, and a YZ-plane without changing a relative position of one of the tool attacher (110; 210) and the work attacher (120; 220) to which said image capturer (101; 201; 501) is attached, and to change the relative position of one of the tool attacher (110; 210) and the work attacher (120; 220), to cause the image capturing element at the second position (112; 312; 512) and the image capturing element at the third position (113; 313; 513) to capture the first point (121; 321), to cause the image capturing element at the first position (111; 311; 511) and the image capturing element at the third position (113; 313; 513) to capture the second point (122; 322), and to cause the image capturing element at the first position and the image capturing element at the second position to capture the third point (123; 323); and a calculator (103; 303) that is configured to calculate a value indicating the planar relative motion between the tool attacher (110; 210) and the work attacher (120; 220) based on an image capturing result of said image capturer (101; 201; 501).