A sheet binding device includes a pressurizing unit that pressurizes a sheet bundle to bind the sheet bundle, a pressurizing section that is disposed in the pressurizing unit and configured to be moved from a waiting position separated from the sheet bundle to a pressurizing position at which the pressurizing section pressurizes the sheet bundle, a drive motor that actuates the pressurizing unit, and a controller that controls the drive motor such that the pressurizing section is engaged with the sheet bundle at a predetermined setting velocity.