To provide an internally grooved tube, and its manufacturing device and method, capable of smoothing an outer surface free from helical unevenness caused by rolling work, having high adhesiveness to a fin plate, and reducing the cracking in hair pin bending work and the loosening and the like in unwinding LWC.

This internally grooved tube having a helical groove with trapezoidal cross-sectional shape, a lead angle of 25-50° and a crest angle of 10-30°, on its inner face, having a maximum surface roughness in the tube axial direction of the outer surface of 3.2 μm or less, and its average surface roughness of 0.35 μm or less, is manufactured by using a manufacturing device wherein a grooved plug 5 is connected with a holding plug 2 through a plug shaft 4, a plurality of rolling balls 6 are mounted on an outer face of a base tube 1 in a state of being revolvable in the tube circumferential direction on an axis of the base tube 1, a cylindrical member 12 with a flange part is mounted at a downstream side in the tube drawing-out direction with respect to the rolling balls 6, and a surface shaping die 13 and a shaping die 8 are mounted at a downstream side in the tube drawing-out direction with respect to the cylindrical member 12.