An injection valve switches between a first state in which a sample loop is connected to a separation flow path through which a mobile phase from a liquid sender flows and a second state in which the sample loop is disconnected from the separation flow path. A pump speed determiner, in a case where a sample intake operation by a syringe pump is started immediately after the injection valve is switched from the second state to the first state, and a filling operation of filling the sample loop with the sample by the syringe pump is started after the intake operation is completed, determines an intake operation speed of the syringe pump that is required in order for the filling operation to complete immediately before the injection valve is switched from the second state to the first state next time using a set injection interval time. The syringe pump operates at the intake operation speed determined by the pump speed determiner while performing the intake operation. The sample is injected by the injector at intervals of the set injection interval time.