Brush unit and connection device

A brush unit attached to a conductor and abutting on a shaft conductive part provided on a rotary shaft to electrically connect the conductor and the shaft conductive part, the brush unit comprising:

• a holder of a concave shape attached to the conductor, having conductivity, and having an opening part provided on a side of the shaft conductive part;
• a brush accommodated in the holder, abutting on the shaft conductive part via the opening part, and having conductivity, and
• a biasing part having conductivity, arranged between a bottom in the holder and the brush, and biasing the brush toward a side of the opening part, wherein
• the brush includes:
• a first brush part having an abutting surface abutting on the shaft conductive part;
• and
• a second brush part having one end portion connected to the first brush part and the other end portion biased by the biasing part,
• the second brush part having an outer shape larger than an outer shape of the first brush part in a direction orthogonal to a biasing direction of the biasing part,
• the holder includes a projecting part projecting inward from the opening part, and
• the projecting part being opposed to a surface of the second brush part to which the first brush part is connected in the biasing direction of the biasing part.