To manufacture a high-quality welded pipe, there is provided a welded pipe manufacturing apparatus for manufacturing a welded pipe by bending a metal plate and welding butting end portions of the metal plate. The welded pipe manufacturing apparatus includes a bending unit that bends the metal plate, a light emitter that emits directional light to an inner surface of the metal plate bent by the bending unit, an image capturing unit that captures light emitted by the light emitter and reflected by a surface of the metal plate, and an adjustment assistance unit that assists adjustment of the bending unit in accordance with a shape of the reflected light.