Abstract: In order to make good-quality concrete, a concrete mixer for mixing materials of concrete by rotation is provided so as to enhance fluidity of a mixture. A mounting frame 7 supporting a drum 2 of a concrete mixer 1 fixes a vibration device 25 via a mounting plate 21. A pair of arms 20 is integrally formed with both ends of the mounting plate 21, while rollers 24 rotationally supported by one ends of the arms 20 respectively contact the outer periphery of the drum 2. A vibration of the vibration device 25 is transmitted from the rollers 24 rotatably supported by the pair of arms 20 to the drum 2, so that the drum 2 vibrates while it rotates. Accordingly, a mixture is liquefied, and thus concrete having a good quality can be produced.