Construction machine

A construction machine, having a vehicular lower structure, and an upper revolving structure swingably mounted on said vehicular lower structure, having a cab mounted on a front side of a revolving frame which constitutes a sturdy support structure;

• said cab being composed of a floor member mounted on said revolving frame and including a floor panel, a right-hand side panel located at a right side of said floor panel and a rear partition panel located in a rear side section of said floor panel, a seat support platform mounted on said floor panel of said floor member to support thereon an operator's seat to be taken by an operator, said seat support platform internally defining an air conditioner unit accommodation space, a cab box built on said floor member to define an operator's dwelling space around said operator's seat and provided with an entrance way in left one of right and left side faces, and an air conditioner unit installed in said air conditioner unit accommodation space to condition intake air and to supply conditioned air to said cab box, characterized in that:
• an under floor duct is provided on the lower side surface of said floor panel of said floor member to form an external air induction passage to supply external air to said air conditioner unit from outside said cab;
• an external air inlet port being provided in a lower portion of a right-hand side panel of said floor member, at the opposite side from said entrance way of said cab box, to let external air flow into said under floor duct;
• and
• an external air outlet port being provided in a lower portion of a rear partition panel of said floor member, to let external air flow out from said under floor duct to said air conditioner unit.