Based on a conveyance amount in a second conveyance state where a sheet is conveyed by both a first conveyance unit and a second conveyance unit being a conveyance amount obtained by subjecting a conveyance amount in a first conveyance state where the sheet is conveyed only by the first conveyance unit and a conveyance amount in a third conveyance state where the sheet is conveyed only by the second conveyance unit to weighted average with difficulty of slipping of the first or second conveyance unit to the sheet as a weighting coefficient, a remaining conveyance amount is calculated from any two conveyance amounts from among conveyance amounts of the first, the second and the third conveyance states, and a correction value for conveyance is set from the calculated conveyance amount.