A ground source heat pump is attracting attention as a technology to save energy. In this study, we have carried out the experiment using a ground source heat pump that uses direct expansion method. 12 underground heat exchangers were inserted into the foundation piles. We obtained a coefficient of performance by measuring an amount of transferred heat and an electricity consumption. The objective of this study is to evaluate the performance during cooling and heating air conditioning using direct expansion method ground source heat pump that utilize foundation steel pipe piles for house. From the experimental result obtained, the COP was approximately 4.0 in the cooling operation and the COP was approximately 4.8 in the heating operation. In addition, performance deterioration was not observed in the intermittent cooling / heating operation for 5 days.