There is provided a printing apparatus including: a printing section; a transport mechanism in which a transport route and a re-transport route are formed, the transport mechanism including an install section to which a transport unit is to be installed; and a print control section which controls the printing section and the transport mechanism to execute a plurality of kinds of double-sided printing processes having different maximum numbers of sheets present at the same time in the transport mechanism from each other so that in a case that the transport unit is installed to the install section, a double-sided printing process in which a maximum number of sheets is large as compared with a case in which the transport unit is not installed to the install section is executed.