It is a challenge for all-optical switching to simultaneous achieve ultralow power consumption, broad bandwidth and high extinction ratio. We experimentally demonstrate an ultralow-power all-optical switching by exploiting chiral interaction between light and optically active material in a Mach-Zehnder interferometer. We achieve switching extinction ratio of 20.0 ± 3.8 and 14.7 ± 2.8 dB with power cost of 66.1 ± 0.7 and 1.3 ± 0.1 fJ/bit, respectively. The bandwidth of our all-optical switching is about 4.2 GHz. Moreover, our all-optical switching has the potential to be operated at few-photon level. Our scheme paves the way towards ultralow-power and ultrafast all-optical information processing.