An armature including magnetic cores arranged on a surface of a plate, coils provided around the magnetic cores, and a magnetic material plate having a plurality of first magnetic members is characterized in that the magnetic material plate is attached to a surface on the opposite side to a surface where the magnetic cores and the plate come in contact, a gap is provided between each of the first magnetic members adjacent to each other, and the area of a surface where the first magnetic members come in contact with the magnetic cores is larger than the area of a surface where the magnetic cores come in contact with the first magnetic members.