To prevent ink mist from sticking to a linear encoder scale and a linear encoder sensor while intending to simplify, save space, save cost.

An image forming device has an image forming device body 1 having a linear encoder scale 91 mounting a liquid discharge head 34 discharging ink on a carriage 33, reciprocally moving the same in a main scanning direction, conveying sheets 42 in a sub scanning direction perpendicular to the main scanning direction, and for detecting the position of the carriage 33 in the main scanning direction, and a linear encoder sensor 92; and a both surface unit 71 connected to the image forming device body 1 and reversing the recording surface of the sheets 42. The both surface unit 71 has a ventilation opening 110 communicating the inside and the outside, a communicating opening 111 communicating with the image forming device body 1, an air flowing channel 115 through which air flows, and a fan 112 forming an air flow, and conveys the sheets 42 between the both surface unit 71 and the image forming device body 1 through the communicating opening 111.