A magnetic gear mechanism including a simplified assembly of a magnetic flux modulating section in the magnetic gear mechanism which improves the strength thereof. In the magnetic flux modulating section of the magnetic gear mechanism, the magnetic flux modulating section being formed of a magnetic member and a non-magnetic member, a piece of the magnetic member and a piece of the non-magnetic member are separately produced. The piece of the magnetic member is sandwiched between circumferential projections provided in pieces of the non-magnetic member, and the magnetic member and the non-magnetic member and bearing holding sections form a structure in which the magnetic member and the non-magnetic member are fitted into the bearing holding sections by using recessed portions provided in the bearing holding sections and axial projections provided in the pieces of the non-magnetic member. This structure simplifies production and improves strength.