To connect a boom cable to a cable at the car body side together by utilizing a configuration adopting a fixed barrel and a movable barrel for inserting a concrete transfer pipe through the center of a slewing joint in this slewing connection apparatus.

This apparatus has a slewing barrel combined to a fixed barrel attached to the car body and a fixed barrel attached to a slewing frame in a slewing manner and is equipped with a slewing joint through which the concrete transport pipe is inserted to and arranged at the inner side of one barrel combined to the inner side, a ring-shaped fixed main body arranged surrounding the environs of the fixed barrel and a fixed contact body having a fixed contact to which a cable provided at the car body side along the peripheral direction is connected to a ring-shaped main body, and a movable contact body having a movable contact provided at the movable main body slewing with the slewing barrel in one united body and a movable contact which is provided at the movable main body and slews together with the slewing barrel and slides on the fixed contact connected to a cable at the boom side in the configuration.