A swash-plate compression device of the variable capacity type used in a refrigerating system of a vehicle comprises a swash-plate compressor and a control valve for autonomously adjusting the pressure in a crank chamber of the compressor. The control valve is opened and closed to introduce some of a refrigerant, which is discharged from the compressor, into the crank chamber. The opening of the control valve is controlled in accordance with a target differential pressure between the actual discharge pressure of the discharged refrigerant and the mean internal pressure of the entire compression chambers of the compressor or between the actual discharge pressure and the peak value of the internal pressure of the compression chamber so that the actual capacity of the compressor is feedback-controlled to be adjusted to a target capacity therefor.