To allow the device to attach/detach a line scanner section to/from a serial printer section.

In the case of detachably mounting a printer section 200 onto a printer section 401, the scanner section is mounted to a guide member of a carrier 2. Furthermore, the scanner section is mounted after the carrier 2 is moved to an escaping position, opposite to the home position. Through this constitution, the scanner section is mounted onto the printer section with high accuracy and a flexible cable 3 connecting to the carrier 2 does not project, thereby attaining ease of mount.