A PCV valve is arranged in an outflow passage. An ECU controls rotation of a motor such that an opening degree of the PCV valve increases in response to an increase in an opening degree of a throttle valve. The outflow passage connects an interior of a head cover of an engine to a portion of an intake air passage located on a downstream side of the throttle valve. The outflow passage recirculates blow-by gas leaked from a combustion chamber into an interior of a crankcase to the portion of the intake air passage located on the downstream side of the throttle valve. An inflow passage connects the interior of the head cover to a portion of the intake air passage located on an upstream side of the throttle valve. The inflow passage conducts intake air from the intake air passage to the interior of the head cover.