In a farmer's strawberry greenhouse, seasonal changes in solar radiation and air conditions (temperature, humidity and CO2 concentration) were measured, and it became clear that the stable yearround production of strawberry was depressed by low temperature and low solar radiation in the cold season and excessively high daytime temperature in the warm season. Furthermore, dew formation in the nighttime, excessively low humidity in the fair daytime and the inappropriate application of CO2 enrichment were also concerned with the depression of stable production. Therefore, a local environment control system was newly developed on the basis of the air circulation and the heat exchange between the constant soil temperature layer and strawberry inter-rows. The system was composed of an underground air pipe (UAP) and inter-row air ducts (IAD) connected to UAP, and UAP was set at a depth of 1.5m where the soil temperature is kept around a temperature suitable for the strawberry growth all the year round. The system can be expected to enable the energy-saving and local control of the ambient air condition of strawberry crops for the stable year-round production.