A thread shape dimension measuring device which measures a thread shape dimension of a threaded portion in a threaded pipe having the threaded portion formed at an end portion and on which a pair of flank surfaces defining each thread ridge of the threaded portion are both formed in an overhanging manner in a view seen in a cross section including a pipe axis, the thread shape dimension measuring device comprising an illumination unit, an imaging unit, a focal distance adjustment unit, a calibration value setting unit, and a control unit, wherein the illumination unit is disposed to face the imaging unit, and selectively emits parallel light in two directions including a first illumination direction, which is one direction, and a second illumination direction, which is another direction, with a direction in which the imaging unit is seen from the illumination unit interposed therebetween, the imaging unit selectively performs capturing of a first captured image by receiving the parallel light from the first illumination direction and capturing of a second captured image by receiving the parallel light from the second illumination direction, the focal distance adjustment unit adjusts a focusing position of the imaging unit by receiving an adjustment instruction from the control unit, the calibration value setting unit has a difference value between a focal distance of the second captured image from the focusing position to the imaging unit before the focusing position adjustment and a focal distance of the first captured image from the focusing position to the imaging unit, and the control unit acquires the difference value from the calibration value setting unit, gives the adjustment instruction to bring the focusing position closer to the illumination unit by the difference value to the focal distance adjustment unit when the second captured image is captured, and calculates the thread shape dimension on the basis of the captured first captured image and the second captured image. the illumination unit is disposed to face the imaging unit, and selectively emits parallel light in two directions including a first illumination direction, which is one direction, and a second illumination direction, which is another direction, with a direction in which the imaging unit is seen from the illumination unit interposed therebetween, the imaging unit selectively performs capturing of a first captured image by receiving the parallel light from the first illumination direction and capturing of a second captured image by receiving the parallel light from the second illumination direction, the focal distance adjustment unit adjusts a focusing position of the imaging unit by receiving an adjustment instruction from the control unit, the calibration value setting unit has a difference value between a focal distance of the second captured image from the focusing position to the imaging unit before the focusing position adjustment and a focal distance of the first captured image from the focusing position to the imaging unit, and the control unit acquires the difference value from the calibration value setting unit, gives the adjustment instruction to bring the focusing position closer to the illumination unit by the difference value to the focal distance adjustment unit when the second captured image is captured, and calculates the thread shape dimension on the basis of the captured first captured image and the second captured image. acquires the difference value from the calibration value setting unit, gives the adjustment instruction to bring the focusing position closer to the illumination unit by the difference value to the focal distance adjustment unit when the second captured image is captured, and calculates the thread shape dimension on the basis of the captured first captured image and the second captured image.