An external control type fan clutch device, the device comprising: a torque transmission chamber incorporating a drive disk therein and provided within a sealed housing composed of a nonmagnetic case and a cover mounted on the case, the case and the cover being supported via bearings (13, 14) on a rotary shaft with the drive disk fixed thereto; at least one oil circulating flow passage hole communicating with a torque transmission gap and provided on a side wall of an oil reserving chamber formed by a hollow in the drive disk; a valve member having magnetism for opening or closing the oil circulating flow passage hole, the valve member having an armature attached to a leaf spring mounted on the drive disk; an electromagnet supported on the rotary shaft via a bearing; and a first ring-like magnetic body disposed on the outer periphery of the rotary shaft via a ring-like nonmagnetic body, wherein opening and closing of the oil circulating flow passage hole is controlled by the valve member actuated by the electromagnet, and rotary torque transmission from a drive side including the rotary shaft to a driven side including the sealed housing is controlled by increasing and decreasing an effective contact area of oil in the torque transmission gap formed between the drive side and the driven side, wherein a second ring-like magnetic body is disposed adjacent to the electromagnet on the outer periphery of the rotary shaft to configure a magnetic circuit for actuation of the valve member, characterized in that the first ring-like magnetic body, the ring-like nonmagnetic body and the second ring-like magnetic body are fixed to the rotary shaft in a rotationally rigid manner and the first ring-like magnetic body and the ring-like nonmagnetic body are disposed radially between the bearing supporting the case and the rotary shaft. a torque transmission chamber incorporating a drive disk therein and provided within a sealed housing composed of a nonmagnetic case and a cover mounted on the case, the case and the cover being supported via bearings (13, 14) on a rotary shaft with the drive disk fixed thereto; at least one oil circulating flow passage hole communicating with a torque transmission gap and provided on a side wall of an oil reserving chamber formed by a hollow in the drive disk; a valve member having magnetism for opening or closing the oil circulating flow passage hole, the valve member having an armature attached to a leaf spring mounted on the drive disk; an electromagnet supported on the rotary shaft via a bearing; and a first ring-like magnetic body disposed on the outer periphery of the rotary shaft via a ring-like nonmagnetic body, wherein opening and closing of the oil circulating flow passage hole is controlled by the valve member actuated by the electromagnet, and rotary torque transmission from a drive side including the rotary shaft to a driven side including the sealed housing is controlled by increasing and decreasing an effective contact area of oil in the torque transmission gap formed between the drive side and the driven side, wherein a second ring-like magnetic body is disposed adjacent to the electromagnet on the outer periphery of the rotary shaft to configure a magnetic circuit for actuation of the valve member, characterized in that the first ring-like magnetic body, the ring-like nonmagnetic body and the second ring-like magnetic body are fixed to the rotary shaft in a rotationally rigid manner and the first ring-like magnetic body and the ring-like nonmagnetic body are disposed radially between the bearing supporting the case and the rotary shaft.