The web conveyor conveys a continuous web for L size or M size. The conveyor includes a guide mechanism changing a passing position of a side edge portion of the web, a detection mechanism detecting the passing position of the edge portion of the web, and a drive mechanism moving the guide mechanism and the detection mechanism together in the cross direction of the web according to the L size or M size, by being in contact with a first side edge portion and a second side edge portion of the web. The drive mechanism moves the guide mechanism and the detection mechanism by an equal traveling distance in the cross direction of the web.
