A sheet folding apparatus includes a sheet transport system, adjustable folding members arranged to bend and fold a sheet fed by the transport system, and a control system arranged to adjust the folding members to set positions in accordance with information on sheet properties. The control system stores a table that specifies different set positions of the folding members for different bending properties of the sheets and is adapted to read information on the bending properties of the sheets to be folded and to adjust the folding members to set positions as specified by the bending properties.