An inspection apparatus for a heat transfer tube is provided in an inspection robot to be fixed to a tube plate surface of a tube plate at which the heat transfer tube is opened and is for inspecting a seal-welded portion at which the heat transfer tube is welded to the tube plate. The inspection apparatus includes: an inserting unit to be inserted into and withdrawn from the heat transfer tube; a detecting unit having detecting unit for detecting the presence or absence of a defect at the seal-welded portion; a rotating mechanism for rotating the detecting unit around a central axis of the inserting unit; and a moving mechanism for moving, with respect to the inspection robot, the inserting unit, the detecting unit, and the rotating mechanism along the central axis for the rotation of the detecting unit.