A sheet conveyer, comprising: a 1st conveying roller; a 1st support part to support the 1st conveying roller; a 1st helical gear to rotate together with the 1st conveying roller and to generate thrust in a particular direction; a 2nd conveying roller; a 2nd support part to support the 2nd conveying roller; a 2nd helical gear to generate thrust in the particular direction; a 3rd helical gear to engage with the 1st helical gear; a 4th helical gear to engage with the 2nd helical gear; and a clutch to connect or disconnect transmission of a driving force between the 3rd helical gear and the 4th helical gear, wherein: when the clutch is disconnected, the 1st and 2nd conveying rollers are disposed at an initial position, and when the clutch is connected, the 1st and 2nd conveying rollers move from the initial position in the particular direction.