A displacement control mechanism for a variable displacement compressor includes a first valve hole, a first valve body, a pressure sensing means operable to sense pressures of first and second points in a discharge pressure region to adjust a position of the first valve body, and a pressure-difference-increasing means operable to increase pressure difference between the first and second points when the pressure of a suction pressure region falls below a predetermined standard pressure. The pressure sensing means displaces the first valve body to increase an opening degree of the first valve hole according to increase of the pressure difference when the first valve hole is part of a supply passage. The pressure sensing means displaces the first valve body to decrease the opening degree of the first valve hole according to the increase of the pressure difference when the first valve hole is part of a bleed passage.