Experiments were conducted to verify whether an Oscillating Heat Pipe (OHP) with reservoir works as a temperature controllable thermal control device in space. We set the reservoir in 3 ways (vertical, horizontal, and vertically inverted directions) and confirmed that the OHP operates as a variable conductance heat pipe in each case. We also put the OHP vertically and confirmed that the OHP works even in the "top heat mode". It is concluded that the OHP does not lose its temperature control function of reservoir and heat transfer function of OHP by gravity.