PROBLEM TO BE SOLVED: To provide a germination promoting device stably promoting germination of seeds.SOLUTION: The germination promoting device is provided with: an airtight container 3 storing water 100 and seeds 101 pressure adjustment parts 2, 4 adjusting injection pressure of oxygen gas injected into the airtight container 3 and a pressure detection part 5 detecting pressure inside the airtight container 3. The pressure adjustment parts 2, 4 refer to the pressure detected by the pressure detection part 5 to press the oxygen gas into the airtight container 3 so as to maintain the water 100 inside the airtight container 3 to be oxygen-supersaturated water.