PURPOSE: To guide a working robot, pressing it to the outer surface on the vessel side without requiring power, by obtaining the force for pressing the working robot to the outer surface on the vessel side from the buoyancy acting to a float.

CONSTITUTION: A working robot pressing guide device is equipped with an inclined stay 8 equipped with a float 9 whose lower edge is pivotally installed in turnable manner an a bracket 7 which bulges out to the outside of the vessel side from a buoyancy type base board 3 equipped with shift devices 5, 5', and 6 for changing the press contact position, straightly erecting guide rail 10 which is supported by the stay 8 and guides a working robot 2, pressing it to the outer surface on the vessel side, and a buoyancy adjusting device 11 for increasing/decreasing the buoyancy by sending the compressed air into the buoyancy tanks 4 and 4' of the base board 3 and the float 9 of the stay 8. The pressing of the working robot 2 to the outer surface on the vessel side is carried out by utilizing the turning force to an erection state of the stay 8 by the buoyancy of the float 9.