An excitation operation brake (1) comprising:a braking shaft (2) serving as a braking target member;an armature (9) attached to the braking shaft (2) such that the armature (9) rotates integrally with the braking shaft (2);a field core (31) including a disc (21) facing the armature (9) in an axial direction of the braking shaft (2), and an annular groove (41); andan exciting coil (42) stored in the annular groove (41) of the field core (31),wherein the disc (21) forms a magnetic flux path that makes a magnetic flux generated by energizing the exciting coil (42) flow in a radial direction of the disc (21),the disc (21) includes a plurality of magnetic shielding portions (47, 48) that make the magnetic flux bypass to the armature (9) a plurality of times, andof the plurality of magnetic shielding portions (47, 48), an outer magnetic shielding portion (47) located on an outer side in the radial direction includes a bypass magnetic path (71) having a magnetic resistance smaller than a magnetic resistance of a magnetic path that bypasses the armature (9).