To provide a sea bottom sitting type geological sampling device which is lightweight and excellent in workability and can stably sit on the sea bottom.

The device is for geological sampling by a boring machine (not illustrated ) loaded on a frame 1 sitting on the sea bottom such as the ocean bed. An adsorption part 4 forming a hermetically sealed room 5 between the frame 1 and the sea bottom 2 is provided, and a pump 7 sucking and discharging the water in the adsorption part 4 is provided. By operating the pump, the water in the room 5 of the adsorption part 4 is sucked and discharged. So a pressure difference between the inside and the outside of the room 5 occurs and a pressing force to the sea bottom 2 generates in the adsorption part.