PROBLEM TO BE SOLVED: To suppress reduction of lifetime or occurrence of failure of a built-in battery in a farm field observation apparatus which observes environment of a farm field.SOLUTION: A farm field observation apparatus comprises an apparatus body 2 and an underground embedded part 3. A sensor 7 measures predetermined physical quantity of a farm field. A battery 10 supplies electric power to the sensor 7, a control part 13 which processes an output from the sensor 7, and the like. The battery 10 is arranged inside the underground embedded part 3 and in an area where the underground embedded part 3 is positioned underground when it is embedded underground. Because underground temperature is more stable than air temperature, the temperature of the battery 10 is stabilized affected by underground temperature.
