A driving device includes a drive source, a driving unit, and a driven member. The drive source is configured and arranged to generate a driving force. The driving unit is coupled to the drive source to move with a reciprocating motion between first and second directions by the driving force. The driven member is arranged to frictionally engage with the driving unit to move in the first direction in response to the reciprocating motion of the driving unit. The driving unit is further arranged to convert a portion of the driving force into a pressing force that acts on the driven member in a direction substantially perpendicular to the first and second directions with a first conversion ratio when the driving unit moves in the first direction and with a second conversion ratio smaller than the first conversion ratio when the driving unit moves in the second direction.