provided is an apparatus for inspecting a structure including a heating tube , a tube sheet supporting the heating tube , and a flow distribution baffle , which are installed in a steam generator of a nuclear power plant , and more particularly , an apparatus for visually inspecting and removing a foreign object in gaps of a bundle of heating tubes of an upper portion of a tube sheet of a secondary side of a steam generator , in which a detector is inserted into gaps of a bundle of heating tubes of an upper portion of a secondary side of a steam generator so as to inspect sludge or foreign objects , and a foreign object remover removes foreign objects when foreign objects are discovered in the gaps of the heating tubes .