To detect a liquid leakage in the whole system of a liquid chromatograph device not by using a flow sensor but by using another means.

A pressure value in a flow path increases when a mobile phase is continuously sent by a feed pump 1 with the flow path closed by a flow-path opening/closing mechanism 4. The pressure value reaches, sooner or later, a beforehand-set upper limit value of a pressure sensor 2 if no liquid leakage has occurred. If a liquid leakage has occurred in the flow path, however, a pressure increase in the flow path falls short of the upper limit value of the pressure sensor 2 because of a pressure loss at a leakage point. While continuously sending the mobile phase by the feed pump 1 with the flow path closed by the mechanism 4, a pressure in the flow path is measured after a definite period of time and compared with the upper limit value of the pressure sensor beforehand set by a liquid leakage determination part, thereby determining whether or not a liquid leakage exists in the flow path.