Abstract: A bearing wear detecting device for canned motor driven pumps is disclosed. The device comprise a rotary shaft of a canned motor driven pump having a hole extending in an axial direction from one end of said rotary shaft; an enlarged chamber formed in said hole at a position distant apart from said one end of said rotary shaft by a given distance and having a diameter larger than that of said hole and forming shoulders at boundaries between said hole and said enlarged chamber; and a hermetically sealed pipe provided at its one end with an enlarged sensitive portion and at another end an indicator; said enlarged sensitive portion being enclosed in said enlarged chamber of said rotary shaft. To the one end of the rotary shaft may be secured an end nut with said hole and said enlarged chamber formed therein. The hermetically sealed pipe may be composed of an indicating part and a detecting part telescopically engaged with each other.