To provide a safe millstone device having a reduced width, millstones of which can be easily cleaned.

This millstone device comprises an upper millstone 13 and a lower millstone 12, and the upper millstone 13 is rotated and is placed on and in slide contact with the lower millstone 12. The lower millstone 12 is provided with a through hole penetrating the lower millstone 12 in vertical directions, and the upper millstone 13 is provided with an engagement part at a part corresponding with the through hole, and a rotation shaft is inserted in the through hole, and an engagement part to be engaged with the engagement part of the upper millstone 13 from a lower side is provided on one end of the rotation shaft so as to transmit rotational force of the rotation shaft to the upper millstone 13, and another end part of the rotation shaft penetrates a placement part on which the upper millstone 13 is placed and is extended downwardly of the placement part, and an extension part extended downwardly of the placement part is connected with a drive device 17 for rotatively driving the rotation shaft.