An upper rotating body (3) comprises: a rotating frame (5); a floor member (9) disposed on the rotating frame (5), the front side of the floor member (9) serving as a footrest (11) on which an operator places his/her foot; a cab box (17) forming an operator cab (18) on the floor member (9); and an indoor unit (23) disposed on the floor member (9) for supplying sucked air for the purpose of air conditioning. A lower surface (11B) side of the footrest (11) of the floor member (9) is formed as a unit attachment surface (12), and the indoor unit (23) is installed by placing a box body (24) under the unit attachment surface (12) and, in this state, attaching the box body (24) to the unit attachment surface (12) by using a plurality of bolts (32).