To provide a pipe, a pipe inner wall surface condensation preventive method using the same and a ground heat exchanger using the pipe, usable in various devices as a pipe for making gas flow, and capable of preventing the occurrence of condensation on the inside and propagation of mold.

This moisture absorbing-releasing functional pipe 1 is provided by arranging a humidity adjusting layer including a high absorptive polymer on an inner wall surface of the pipe for making the gas flow, The pipe inner wall surface condensation preventive method is characterized by repeating an absorbing step of absorbing and holding steam included in the gas A flowing in the moisture absorbing-releasing functional pipe 1 in and by the humidity adjusting layer 4, and a releasing step of releasing moisture held inside the humidity adjusting layer 4 to the gas B flowing in the moisture absorbing-releasing functional pipe 1, in a process of taking and flowing the gas in the moisture absorbing-releasing functional pipe 1, by using the moisture absorbing-releasing functional pipe 1 as the pipe.