To provide a drier of an air filter unit capable of efficiently drying the cleaned air filter unit.

This drier 10 has a blowout port for supplying heated air to an inside space, and exhaust ports 17 and 18 arranged under the blowout port, and exhausting the air from the inside space. The cleaned air filter unit 2c is substantially arranged between the blowout port and the exhaust ports 17 and 18 in the vertical direction in the inside space. The air filter unit 2c is desirably arranged in the inside space so that a main surface of a brazing material substantially vertically arranged to a flow of air in use, extends in the substantially horizontal direction.