A device for high-pressure treatment, in particular of liquid substances which contain components with a consistency different from that of the liquid. The device comprises a cylinder member (1), two end members (2, 3), a high-pressure piston (4), two high-pressure seals (8, 9) and connection means comprising channels and valve members to conduct the substance to and from the cylinder member (1). When the substance is pressurized, the cylinder member (1), at least one of the end members (3), the high-pressure piston (4) and the two high-pressure seals (8, 9) delimit a high-pressure chamber (10). The connection means are arranged outside the high-pressure chamber and preferably in respective end members (2, 3).