PURPOSE: To make it possible to carry out working in a frozen sea area, by providing ice-breaking protectors of truncated cone shapes in the lower part of an elevating bed in a platform of jack-up type, around positions in which a plurality of legs and a riser pierce through the elevating bed.

CONSTITUTION: An elevating bed 1 is attached thereto with a plurality of legs 3 by means of elevating devices 2 and as well provided with a riser 6 which is coupled to digging equipment. Truncated cone shape protectors 8 are attached to the parts in the lower part of the elevating bed 1 in which legs 3 and a riser 6 pierce through the elevating bed 1, so that ice plates surging upon the protectors 8 are lifted up along the inclined surfaces thereof, and are broken under surging force by the ice plates themselves. Thereby, working in a frozen sea area with the use of a jack-up type platform is made possible.