To provide a polymer insulator whose life is prolonged by reinforcing the outer coating part near a line side where deterioration proceeds most quickly and suppressing the deterioration.

This polymer insulator 1 comprises a FRP rod 2, an insulating outer coating 3 made of rubber and formed in the outer circumference of the FRP rod 2, and a holding metal tool 4 fixed in an end part of the FRP rod 2 by caulking. In this case, a reinforcing part 11 to prolong the life of the insulating outer coating 3 in the line side, which receives high electric field stress. Alternatively, the part 11 is made of a low temperature vulcanized rubber or a highly elastic rubber.