Abstract: A power antenna for automatically stopping an electric motor when a telescoping trouble occurs with the antenna to thereby cause a load of more than a predetermined magnitude to be applied to the electric motor and preventing the electric motor from being burned out and a telescoping operating mechanism from getting damaged, whereby the occurrence of an erroneous operation of the antenna such as repeated contracting and expanding operations thereof can be controlled. A worm wheel (2) inside an antenna mechanism is pivotally supported in such a manner as to slide in an axial direction and an engagement groove (21) is formed in an annular fashion, and an operating portion (32) of a movable body (17) of a limit switch (30) provided in a driving circuit for the motor is brought into engagement with the engagement groove (21) of the worm wheel.