To always support an opening/closing body by a desired bounce by a gas spring regardless of the change of an environmental temperature used, by only using a simple constituent part as a temperature compensating controller.

In this gas spring 1 by which an opening/closing body attached to be opened and closed to a main body part by using a hinge is supported around the hinge while being energized to an opening direction, a heating element 18 is mounted on the outer wall surface of a cylinder 2 in the gas spring 1, and this heating element 18 is connected to a power supply 20 by an electric circuit 19, and also a normally opened thermal switch 21 which is switched on below a set temperature and a normally closed thermal switch 22 which is switched off when the gas spring 1 reaches a desired temperature, are interposed in series on the way to the electric circuit 19.