There are many bored hot springs showing a geyser-like phenomenon in Japan, and their temperatures do not attain to the boiling point of water. Its mechanism is not explained by the boiling of deep water in a vertical pipe as usual, but they contain much gases, such as methane or carbon dioxide, which are said to be the main role in geyser like mechanism. The present authors tried to explain it with the aid of a model. When there is supplied with some gases at the bottom of water column, the water dissolve it upward from the bottom. Through the water column saturated with gas, the following gas bubbles pass up freely and cause the water level to rise in the pipe. When the water flows over the pipe head, the dissolved gas will be free from the water and expand, and will rush out of the pipe. The rising height of water level and the time interval of the rest relate to the amount of gas supply and to the difference between the pipe head and water level. Some mathematical treatment is procedured.