A pipe thickness measuring device comprising: a luminance profile obtaining unit which obtains luminance profiles in a direction crossing a pipe to be measured from radiographic images of the pipe; an outer diameter point detecting unit which includes a differential profile calculating unit which calculates a first order differential profile by first order differentiating the luminance profile obtained by the luminance profile obtaining unit, or calculates a second order differential profile by second order differentiating the luminance profile obtained by the luminance profile obtaining unit; a noise removing unit which removes noise components from the first order differential profile or the second order differential profile calculated by the differential profile calculating unit; and which detects outer diameter points of the pipe based on a maximum value or a minimum value of the first order differential profile from which the noise components have been removed, or a zero cross point of the second order differential profile from which the noise components have been removed; a region setting unit which sets a predetermined region inside two of the outer diameter points of the pipe which have been detected by the outer diameter point detecting unit and are taken as endpoints of the region; and an inner diameter point detecting unit which detects inner diameter points of the pipe based on a minimum value of a luminance profile corresponding to the set predetermined region from among the luminance profiles obtained by the luminance profile obtaining unit, or a zero cross point of the first order differential profile corresponding to the set predetermined region from among the first order differential profile calculated by the differential profile calculating unit or a maximum value of the second order differential profile corresponding to the set predetermined region from among the second order differential profile calculated by the differential profile calculating unit. a luminance profile obtaining unit which obtains luminance profiles in a direction crossing a pipe to be measured from radiographic images of the pipe; an outer diameter point detecting unit which includes a differential profile calculating unit which calculates a first order differential profile by first order differentiating the luminance profile obtained by the luminance profile obtaining unit, or calculates a second order differential profile by second order differentiating the luminance profile obtained by the luminance profile obtaining unit; a noise removing unit which removes noise components from the first order differential profile or the second order differential profile calculated by the differential profile calculating unit; and which detects outer diameter points of the pipe based on a maximum value or a minimum value of the first order differential profile from which the noise components have been removed, or a zero cross point of the second order differential profile from which the noise components have been removed; a region setting unit which sets a predetermined region inside two of the outer diameter points of the pipe which have been detected by the outer diameter point detecting unit and are taken as endpoints of the region; and an inner diameter point detecting unit which detects inner diameter points of the pipe based on a minimum value of a luminance profile corresponding to the set predetermined region from among the luminance profiles obtained by the luminance profile obtaining unit, or a zero cross point of the first order differential profile corresponding to the set predetermined region from among the first order differential profile calculated by the differential profile calculating unit or a maximum value of the second order differential profile corresponding to the set predetermined region from among the second order differential profile calculated by the differential profile calculating unit.