Abstract: An intake and exhaust system includes an engine, an intake air channel, an exhaust gas channel, an EGR channel, an EGR valve, and a control device. By adjusting an opening degree of the EGR valve, the control device executes EGR control processing to control a flowrate of a recirculating exhaust gas. An isolation valve is disposed in the EGR channel closer to the exhaust gas channel than the EGR valve is. An air admittance valve is disposed in the EGR channel closer to the exhaust gas channel than the EGR valve is and closer to the intake air channel than the isolation valve is. The control device executes learning processing to learn a relationship between an actual flowrate and a reference flowrate while the isolation valve is closed and the air admittance valve is opened. The control device executes the EGR control processing based on a learning processing result.