To provide a rainwater permeation type underground heat exchange system returning rain water into the ground, and capable of efficiency carrying heat exchange by geothermal heat.

A permeation basin 140 is provided on a top part of a heat exchange well 150 disposed with a circulation pipe formed toward the ground and circulating a coolant or a heating medium in an interior, and a water permeation means 160 is provided for promoting heat exchange by permeating water such as rainwater to the permeation basin 140.