A combination of a protective cover having a cup shape, and a bearing device, the bearing device including: a bearing including, on an outer peripheral surface thereof, an inner ring having an inner ring raceway surface; an outer ring, on an inner peripheral surface thereof, having an outer ring raceway surface; and a rolling element rolling between the inner ring raceway surface and the outer ring raceway surface; a magnetic encoder including N poles and S poles, which are alternately arranged at regular intervals in a circumferential direction, the magnetic encoder being located at an inward-side end portion of the bearing and fixed to the inner ring; and a magnetic sensor being opposed to magnetic poles of the magnetic encoder, for detecting rotation of the magnetic encoder, the protective cover having a portion being configured to be mountable to the outer ring so as to seal the inward-side end portion of the bearing, the protective cover comprising: a disc part made of a synthetic resin; a sensor holder part made of the synthetic resin and protruding inward from the disc part in a direction away from and opposite to the portion mountable to the outer ring, wherein the magnetic sensor is attached to the sensor holder part; and a protruding part made of the synthetic resin, protruding inward from the disc part, in the direction away from and opposite to the portion mountable to the outer ring, via an outward-side face of the protruding part to an inward-side face of the protruding part, to be continuous with the sensor holder part, the protective cover being molded through injection molding of the synthetic resin, the sensor holder part of the disc part having a separation wall which is thinner than other portions of the disc part and separates the magnetic encoder and the magnetic sensor from each other, the protruding part having, at the inward-side face thereof, on the side opposite to the portion mountable to the outer ring, a gate mark caused by the injection molding, the protruding part being provided with a thickness reduction part extending inward, in the direction away from and opposite to the portion mountable to the outer ring, from the disc part to the outward-side face thereof so as to be close to the gate mark. a bearing including, on an outer peripheral surface thereof, an inner ring having an inner ring raceway surface; an outer ring, on an inner peripheral surface thereof, having an outer ring raceway surface; and a rolling element rolling between the inner ring raceway surface and the outer ring raceway surface; a magnetic encoder including N poles and S poles, which are alternately arranged at regular intervals in a circumferential direction, the magnetic encoder being located at an inward-side end portion of the bearing and fixed to the inner ring; and a magnetic sensor being opposed to magnetic poles of the magnetic encoder, for detecting rotation of the magnetic encoder, the protective cover having a portion being configured to be mountable to the outer ring so as to seal the inward-side end portion of the bearing, the protective cover comprising: a disc part made of a synthetic resin; a sensor holder part made of the synthetic resin and protruding inward from the disc part in a direction away from and opposite to the portion mountable to the outer ring, wherein the magnetic sensor is attached to the sensor holder part; and a disc part made of a synthetic resin; a sensor holder part made of the synthetic resin and protruding inward from the disc part in a direction away from and opposite to the portion mountable to the outer ring, wherein the magnetic sensor is attached to the sensor holder part; and a protruding part made of the synthetic resin, protruding inward from the disc part, in the direction away from and opposite to the portion mountable to the outer ring, via an outward-side face of the protruding part to an inward-side face of the protruding part, to be continuous with the sensor holder part, the protective cover being molded through injection molding of the synthetic resin, the sensor holder part of the disc part having a separation wall which is thinner than other portions of the disc part and separates the magnetic encoder and the magnetic sensor from each other, the protruding part having, at the inward-side face thereof, on the side opposite to the portion mountable to the outer ring, a gate mark caused by the injection molding, the protruding part being provided with a thickness reduction part extending inward, in the direction away from and opposite to the portion mountable to the outer ring, from the disc part to the outward-side face thereof so as to be close to the gate mark.