The object of the present invention is to provide an electric construction machine capable of efficiently cooling the battery mounted on the swing structure. To achieve the object, there is provided an electric construction machine in which a battery storage room 11 is formed in the swing structure 3 and a plurality of batteries 231 as electric power sources are arranged in the battery storage room 11, comprising: a battery storage structure 23 storing the batteries 231 and having an air flow channel through which air can flow upward from a lower part of the battery storage structure 23; a covering sheet 26 entirely covering the top and side faces of the battery storage structure 23; and a duct 27 for discharging the air, one end of which is arranged in an upper part of the covering sheet 26.