Provided is a duct which is installed adjacent to a wall-type air conditioner to pass through a pipe connected to the air conditioner, which includes a base housing installed on a wall surface adjacent to the air conditioner, a horizontal partition wall disposed at the front side of the base housing to divide the inside of the duct into an upper space and a lower space, an upper housing covering the upper space, a translucent reservoir detachably mounted on a lower portion of the horizontal partition wall in response to the lower space and collecting condensed water generated from the air conditioner through an inlet formed in the horizontal partition wall, and a pump module installed in the upper space to discharge the condensed water collected in the reservoir. The reservoir is positioned below the upper housing and the horizontal partition wall to be always exposed to the outside.