A form measuring apparatus configured to perform measurement of a form of an object having a three-dimensional form, the apparatus comprising: a detecting section which is configured to perform detection of the form of the object having the three-dimensional form; an area-setting section which is configured to set, as a measurement area, an outside area located outside of a designated area of the object, wherein the area-setting section includes: an internal-interpolation processing section which is configured to obtain an approximate curve line between positions (P1, P2, P3) of the designated area by internal-interpolation processing based on the form detected at the positions of the designated area; and an external-interpolation processing section which is configured to perform an extrapolation processing based on the approximate curve line obtained by the internal-interpolation processing in order to calculate the outside area; the measurement area including a measurement start point (Ps) and a measurement end point (Pe); the measurement area including end portions of the object; wherein the detecting section is configured to perform the detection at the measurement start point (Ps) in the measurement area located outside of the designated area and to thereafter perform the detection in the designated area. a detecting section which is configured to perform detection of the form of the object having the three-dimensional form; an area-setting section which is configured to set, as a measurement area, an outside area located outside of a designated area of the object, wherein the area-setting section includes: an internal-interpolation processing section which is configured to obtain an approximate curve line between positions (P1, P2, P3) of the designated area by internal-interpolation processing based on the form detected at the positions of the designated area; and an external-interpolation processing section which is configured to perform an extrapolation processing based on the approximate curve line obtained by the internal-interpolation processing in order to calculate the outside area; the measurement area including a measurement start point (Ps) and a measurement end point (Pe); the measurement area including end portions of the object; wherein the detecting section is configured to perform the detection at the measurement start point (Ps) in the measurement area located outside of the designated area and to thereafter perform the detection in the designated area. an internal-interpolation processing section which is configured to obtain an approximate curve line between positions (P1, P2, P3) of the designated area by internal-interpolation processing based on the form detected at the positions of the designated area; and an external-interpolation processing section which is configured to perform an extrapolation processing based on the approximate curve line obtained by the internal-interpolation processing in order to calculate the outside area; the measurement area including a measurement start point (Ps) and a measurement end point (Pe); the measurement area including end portions of the object; wherein the detecting section is configured to perform the detection at the measurement start point (Ps) in the measurement area located outside of the designated area and to thereafter perform the detection in the designated area.