A sheet transport apparatus is provided with a processing section, and a first roller pair and a second roller pair disposed at the front and back of the processing section to transport the sheet to the processing section at a predetermined velocity. Each of driving transmission mechanisms respectively for driving the first roller pair and second roller pair is provided with a rotary shaft for supporting the roller, a rotary member provided with a circular fit hole to fit with the rotary shaft, and a holder member in which a D-shaped press-fit hole is formed to press-fit to the rotary shaft, and to the rotary shaft are attached the rotary member with the circular fit hole formed therein and the holder member with the D-shaped press-fit hole formed therein. Then, in attaching the holder member and rotary member to the rotary shaft, a concave portion of the holder member is fitted with a convex portion of the rotary member so that the rotary member and the holder member are substantiallyintegrally coupled. By this means, since driving transferred to the rotary member from a driving motor is transferred to the rotary shaft from the rotary member through the holder member, without def orming the rotary member by stress of the rotary member in attaching to the rotary shaft, it is possible to transfer driving of the rotary member to the rotary shaft with reliability, and the transport rollers are capable of transporting the sheet at a stable velocity without fluctuations in rotation.