To make it possible to monitor a liquid spill in a liquid passage and its generation spot without providing a new pressure sensor, by judging whether there is any liquid spill in the passage, and its spot, from the state of a passage change-over valve by a change-over controlling unit and the pressure of a pressure monitoring unit.

A liquid transfer pump 2 having a pressure sensor 6 transfers a moving phase solvent 4 to a column, and in that moving phase passage a passage change-over valve 8 for an automatic injector is provided. This change- over valve 8 changes passages automatically by a change-over braking unit 10 at the time of sample injection. The output of this pressure sensor 6 is inputted to a pressure monitor 12, and a liquid spill judging unit 14 judges whether there is any liquid spill in a passage, and its spot from the state of the change- over valve 8 by the change-over controlling unit 10, and the pressure of a pressure monitor 12. Namely, if a pressure drops by a magnitude large enough to be able to judge that there is a liquid spill, and if it is at a change-over time of the change-over valve 8, it is judged to be a liquid spill in a part of the injector, and if it is not during a change-over time, it is judged to be a liquid spill at a spot more upstream than the change-over valve 8.