Provided are a clamp jig for inhibiting an increase in the size of clamping equipment, and reducing the load during clamping by clamping after doing preliminary aligning of a segment end part; a stator manufacturing device; and a method for manufacturing a stator. The clamp jig 40 has a pair of clamp bodies 41, extended in a stator core radial direction, for clamping from both sides in the stator core circumferential direction the end part of an electric conductor, which is inserted in the stator core and welded; and a convex part 42 provided extending in the stator core axis direction at the bottom of the clamp body 41, the convex part being inserted between unwelded electric conductors.