A skew correcting device includes a first roller pair configured to nip and convey a sheet, a second roller pair disposed upstream of the first roller pair and configured to nip and convey the sheet, a contact portion disposed downstream of the first roller pair, the contact portion being a portion that the leading edge of the conveyed sheet comes into contact to correct skew of the sheet, a switching mechanism configured to change a nipping force of the first roller pair before the leading edge of the conveyed sheet comes into contact with the contact portion to form a loop in the sheet, and a control unit configured to make a determination on the basis of sheet information as to whether the nipping force of the first roller pair is to be changed, the control unit being configured to control the switching mechanism on the basis of the determination.