A particulate detector is used to detect particulates in gas. The particulate detector includes a housing, an electric-charge generator, a collector, a noise canceller, and a number detection unit. The housing has a gas flow path through which the gas passes. The electric-charge generator applies electric charges generated by electric discharge to the particulates in the gas that is introduced into the gas flow path to obtain charged particulates. The collector is disposed on the gas flow path downstream of the electric-charge generator in a direction of flow of the gas and collects the charged particulates. The noise canceller cancels a noise that is made due to the electric discharge of the electric-charge generator. The number detection unit detects the number of the particulates on the basis of a physical quantity that varies in response to the charged particulates collected by the collector.