A printing device includes a roll paper holder configured to accommodate a first roll paper and a second roll paper and having first and second side walls configured to contact side surfaces of the first roll paper, a remaining amount detecting section having a first projection projecting from the first side wall to detect a remaining amount of the first roll paper accommodated in the roll paper holder, a roll paper guide configured to be installed in the roll paper holder and having a third side wall configured to contact a side surface of the second roll paper when the second roll paper is accommodated in the roll paper holder, and a detection assistance section provided on the roll paper guide and having a second projection projecting from the third side wall in a state of being in contact with the first projection.