An apparatus and a method for adjusting a gap between folding rollers to fold signature in a printing press and the printing press are disclosed. To automatically adjust the gap to the optimum distance through which signatures are passing, the apparatus includes gap adjusting mechanism 17 for adjusting the gap between a pair of folding rollers 14 and 14 to press and fold signature 1, detecting unit 23 for detecting transfer state information relative to actually passing the printed sheets through the gap between the pair of the folding rollers; and controller 24 for controlling the gap adjusting mechanism so that the gap between the folding rollers corresponds to the transfer state information detected by the detecting unit.