A liquid sample analyzing system including an ion analyzer having a first ion source receiving a target sample and a second ion source receiving a reference sample; a liquid sample introduction mechanism 3 including a passage-switching section introducing reference samples into the second ion source; and a controller for repeatedly performing a series of steps in the ion analyzer, the steps including: a pre-measurement step for initiating a measurement; a measurement step for introducing a target sample into the first ion source and performing a measurement on an ion originating from the target sample along with an ion originating from a reference sample introduced into the second ion source by the liquid sample introduction mechanism; and a post-measurement step where the liquid sample introduction mechanism operates concurrently with the predetermined post-measurement step to switch the passage-switching section to a passage having a reference sample for the next analysis.