MAGNETIC POLE PIECE DEVICE AND MAGNETIC GEAR DEVICE

A magnetic pole piece device according to an embodiment is a magnetic pole piece device disposed between an inner diameter side magnet field and an outer diameter side magnet field of a magnetic gear that includes an annular member which includes a plurality of magnetic pole pieces disposed at intervals in a circumferential direction, and a plurality of holding members respectively disposed between the plurality of magnetic pole pieces, and a cover member which is made of a composite material obtained by impregnating continuous fiber extending along the circumferential direction with a matrix resin. The cover member is disposed on at least one of an outer circumferential surface and an inner circumferential surface of the annular member. A relation of ⅙·tc≤t≤½·tc is satisfied, where tc is a gap between the annular member and the magnet field and t is a thickness of the cover member.