A discharge ionization current detector using a low-frequency dielectric barrier discharge with an improved S/N ratio is provided. A current detector 20 is disposed between an excitation high-voltage power source 8 and a discharge electrode 5 to detect a discharge current flowing in pulses due to plasma generation. The detection signal of the current detector 20 and an output signal from a current amplifier 18 for amplifying an ion current are inputted into an output extraction unit 21. The output extraction unit 21 detects a precipitous-rise portion of the discharge current detection signal and generates a trigger signal, and then extracts an ion current signal for a predetermined time period from the trigger signal. This can remove an influence of a noise appearing in a signal during a time period where no plasma emission is generated, thereby improving the S/N ratio of the detection signal.