IMAGE FORMING DEVICE AND IMAGE FORMING METHOD

PROBLEM TO BE SOLVED: To provide an image forming device that is excellent in quietness and improved in productivity in duplex printing.SOLUTION: The image forming device comprises: conveying means that can convey a recording medium 108 in two directions along a sub-scanning direction; a recording head that performs reciprocating scanning in a main scanning direction and forms images on the recording medium being conveyed by the conveying means; inverting means that inverts front and rear sides of the recording medium and conveys the medium to the conveying means; and means for controlling conveyance speed of the recording medium. In duplex printing, during reciprocating conveyance of the recording medium, the recording head forms an image on a first surface of the recording medium, and while the conveying means conveys the recording medium whose front and back sides are inverted by the inverting means and exhausts the medium, the recording head forms an image on a second surface of the recording medium. The control means performs control so that first conveyance speed Vat the time when the first surface is printed in duplex printing and second conveyance speed Vat the time when the second surface is printed in duple printing satisfy a relation of: V≤W/t