The invention relates to a geological self-adaptive extension-type shield tunnel boring machine (TBM) hob device. The geological self-adaptive extension-type shield TBM hob device aims to solve the difficult problems of eccentric abrasion and edge breakage of a hob in the prior art, according to the geological self-adaptive extension-type shield TBM hob device, a cutter shaft of the hob is installed in a cutter seat, and the top of the hob protrudes from the upper surface of the cutter seat; the cutter seat is of a rectangular structure with a holding cavity, and the size of the holding cavityis larger than the size of the hob in the holding cavity; and a floating cutter shaft fixing mechanism is installed in the holding cavity, a floating cutter head fixing mechanism includes at least two sets of hob clamping grooves lifted by a telescopic oil cylinder, the hob clamping grooves include lower part clamping plates and upper part clamping plates which are fixed by bolts, semicircle holes are formed between the lower part clamping plates and the upper part clamping plates correspondingly to install the cutter shaft, the telescopic oil cylinder is provided with a pressure sensor and adistance sensor, and the pressure sensor and the distance sensor are connected with the input end of a controller. The geological self-adaptive extension-type shield TBM hob device has the advantagesthat stress of the hob is changed by adjusting the telescopic oil cylinder, so that all hobs are evenly stressed; and the position of the hob can be adjusted when stress is uneven to avoid the hob bearing a large load or no load.