To provide a brake/clutch unit which carries out the release of the brake and the engagement of the clutch more effectively than a conventional brake/clutch unit.

This brake/clutch unit is furnished with a rotor assembly 12; an armature assembly 16; and a field shell assembly 18. The rotor assembly 12 has a rotor disk 22. The armature assembly 16 has an armature 24; and an output member 26 connected to the armature 24. The field shell assembly 18 has a field shell 30; a pair of permanent magnets 32 and 34; the first and the second magnetic pole pieces 36 and 38 with a low magnetic resistance; the third magnetic pole piece 40 with a high magnetic resistance; and a field coil 42. The third magnetic pole piece 40 is set between the first and the second magnetic pole pieces. The field shell, the permanent magnets, the magnetic pole pieces, and the armature form the first magnetic circuit. By energizing the field coil, the second magnetic circuit is formed.