PURPOSE: To reduce the time for analysis by providing electrode parts before and behind a separating column and migrating and separating a sample in the separating column.

CONSTITUTION: When a sample is supplied to an introducing part 6, the sample is conveyed by a mobile phase to a separating column 7 where the sample is separated to respective components. DC voltage is impressed to electrode parts 3, 4 before and behind the column 7 and the sample is conveyed by the linear speed of the mobile phase plus the migrating speed. The migrating speed is proportional to the impressed voltage. The migrating speed is increased and the time for analyzing the sample is reduced by setting adequately the impressed voltage.