An air pollution control unit is configured to bring particle-containing gas and washing liquid into contact with each other to collect particles in the particle-containing gas. The air pollution control unit includes a gas washing column having a gas cleaning section in which the particle-containing gas and the washing liquid are brought into co-current contact with each other, a gas cooling column disposed downstream of the gas washing column along the gas flow and having a gas cooling section in which the particle-containing gas that has been cleaned (cleaned gas) and cooling liquid are brought into countercurrent contact with each other, and a gas communication path.