To provide a revolving anchor device of a slewing crane for easily fixing a revolving frame by the remote control from an operator's cab.

The revolving anchor device 10 of the slewing crane 1 has an anchor 11 to be freely raised either on the revolving frame 5 or on a base 4 to fix the revolving frame 5, which is rotatable around a standing shaft on the base 4, in a prescribed direction, and an anchor receiver 12 for restricting the horizontal movement of the anchor 11 by engaging with the anchor 11. In the revolving anchor device 10, a plurality of indicators 22 and 23 for indicating the relative positions are disposed at an interval either on the revolving frame 5 or on the base 4, and a plurality of sensors 24 and 25 for detecting the approach of the indicators 22 and 23 are disposed at an interval, different from the interval between the indicators 22 and 23, on the other one of the frame or the base so that the indicators 22 and 23 can be detected at the same time.