In a construction machine, an equipment room cover is formed with a maintenance hole, which has such a shape as to allow an air filter to pass, at a position on a rear side of the air filter mounted to a filter mounting portion of an air intake duct. A locking device of the filter mounting portion has a movable member movable between a locking position and a lock-releasing position. In the locking position, the movable member contacts with a rear surface of the air filter in a state that a front surface of the air filter is contacted with a contact member so that the air filter is sandwiched and held between the movable member and the contact member. In the lock-releasing position, the movable member is moved away from the rear surface of the air filter for allowing movement of the air filter toward the rear side.