PURPOSE: To reduce the insertion resistance of a rotor and facilitate assembling by facilitating injection-molding with the division of a rotary body into a plurality of pieces, and by forming the recessed groove of the rotary body in a tapered shape with the set punching gradient of a metallic mold.

CONSTITUTION: An agitator 10 has a plurality of rotary bodies 29 arranged on a rotary shaft 28, and a sliding contact piece 30 consisting of the flexible materials of rubber and the like in the spiral direction on the outer peripheries of the bodies 29. The rotary body 29 has two projected sections 31 on the one-side surface, and has two recessed sections on the other side surface, and when the body 29 is set on the rotary shaft 28, then the recessed sections 32 and the projected section 31 are engaged with each other. In this case, on a spiral and tapered roughly-recessed groove 33 set on the rotary body 29, a section X and a section Y are arranged at the same position. In order that the width dimension T of the roughly projected section 36 of the sliding contact piece 30 is made almost equal to the minimum width dimension of the tapered section of the mold punching gradient of the recessed groove 33, the rotor 30 is supported by the recessed groove 33 at a contact section 37. Besides, when the projected section 36 is inserted into the recessed groove 33, then insertion resistance is relaxed.