A printer unit includes a device housing including a transport roller and a spreading roller, a roller drive mechanism that is attached to the device housing and includes a drive transmission gear train that drives the transport roller and the spreading roller, and a cover member that covers the roller drive mechanism. The roller drive mechanism includes a gear plate separate from the cover member. The gear plate is fixed to the device housing at two locations and is formed in a plate shape that pivotally supports at least one of rotational shafts of the drive transmission gear train.