SCREW SHAPE MEASURING DEVICE AND MEASURING METHOD

A thread shape measuring apparatus (100) includes: a first illuminating unit (1) that has an optical axis in a direction orthogonal to a cross section M including a thread axis A and emits parallel lights to illuminate the thread portion; a second illuminating unit (2) that has an optical axis in a direction forming an angle θ larger than a lead angle γ of the thread portion with respect to the direction orthogonal to the cross section and emits parallel lights to illuminate the thread portion; an image-capturing unit (3) that has a visual axis parallel to the optical axis of the first illuminating unit (1), includes a telecentric lens (32), has a focusing position matching the cross section, and detects, out of the parallel lights emitted from the first illuminating unit (1) or the second illuminating unit (2), the light that has not been blocked by the thread portion to capture an image of the detected light; and an arithmetic operation unit (4) that arithmetically operates a shape of the thread portion based on a captured image captured by the image-capturing unit (3).