A construction machine including: a lower propelling body; an upper slewing body having a rear region with an engine room; a slewing device for slewing the upper slewing body; and a platform cover. The slewing device includes a slewing electric motor having an electric-motor output shaft, and a speed reducer having a speed-reducer output shaft rotated more slowly than the electric-motor output shaft, the speed reducer installed forward of the engine room such that the speed-reducer output shaft points downward, the slewing electric motor disposed just above the speed reducer. The platform cover is provided on a top of the slewing electric motor, having an upper surface serving as a platform for maintenance of equipment in the engine room. The platform cover is lower than the engine cover and adjacent to a front side of the engine room.