PURPOSE: To surely protect an electric well pump, by attaching a thermosensitive switch to detect both the temperature rise of an electric motor and that of a pump casing.

CONSTITUTION: A thermosensitive switch 40 is mounted on both the flat portion 16 of the flange of the end bracket 13 of an electric motor 10 and the flat portion 25 of a pump casing 20, by inserting a coupling bolt 17 into an opening 45 provided as a bolt relief portion in a mounting metal 44. As a result, both the temperature rise of the electric motor 10 and that of the pump casing 20 can be detected by the same thermosensitive switch 40, and the electric insulation of the switch is kept better.