PURPOSE: To secure stable suction force even if there is any recess on the surface of a suction object.

CONSTITUTION: In this suction device which forms a vacuum chamber whose bottom part is opened, in a suction device body 1 equipped with travel wheels 2 being kept in the fixed distance with a hull outside plate, while installed with a suction fan 5 in a suction port 4 being interconnected to this vacuum chamber 3, a pressure regulating chamber 12 is installed in a side part of the vacuum chamber 3 extending over the whole circumference via a flexible wall body 11, and a spacing member 13, whose tip part comes nearer to the hull outside plate P after making the specified suction opening (d), is installed in a bottom part of this pressure regulating chamber 12, and then air is sealed up in this pressure regulating chamber 12, while the spacing member 13 is constituted so as to be projected according to a pressure rise in this pressure regulating chamber 12.