A construction of a printing apparatus wherein a printing registration with respect to forward and reverse scans of a printing head and a printing registration with respect to a plurality of printing heads are automatically carried out is realized without rendering the apparatus complex or causing its production cost to rise. To this end, the optical sensor for measuring patterns formed for use in printing registration is also used to serve other purposes such as a detection of a printing home position or a detection of a printing medium's end. Furthermore, by appropriately controlling a single optical sensor according to each of various intended purposes, the optimum characteristics are utilized in each respective operating mode. Because of the above, the addition of sensors to be used only for the purpose of printing registration and the accompanying rise of the print apparatus production cost are restrained.